Are you kiting the surges?

Regardless, a lot of guilds use Death Knights and have them pop Icebound Fortitude on every surge and Unbreakable Armor on every other surge. Depending on what trinkets the tank has available, the mitigation and avoidance can both be quite excellent in this manner.

Druids have Barkskin on the same cooldown, but not quite the same level of effectiveness -- due to IBF scaling. That said, druids have strong armor and Survival Instincts on every 3rd surge (and possibly Frenzied Regen on every 3rd surge).

Some guiilds use warriors glyphing shield wall and last stand to ensure one is up for every surge and usually couple the last stand with some kind of avoidance trinket (parry or dodge).

All these refer to non-kite strategies. If you are kiting, it should really not make any difference who tanks.

Whether you use a DK or not, kiting will significantly reduce the damage taken and the amount of mana your healers need spend on keeping your tank up. Not kiting effectively trades healer mana for less complications from shadow crash positioning and complications from moving him in general (such as lower tank threat due to the tank not being able to build threat for 25% of their time). Whether you want to use it depends on what aspect of the fight you are having more problems with. I calculated the relative amounts of damage taken with IBF during kiting or not kiting below to get an idea of the damage difference.

Assuming a kite phase every 60 seconds
Kiting:
3s Casting - No damage
12s Kiting - No damage
12s Icebound Fortitude - 58% damage
33s Normal damage - 100% damage
(12/60 * 0.56 + 33/60 * 1) = 0.662

66.2% overall damage taken

Not kiting:
3s Casting - No damage
10s Surge with IBF - 116% damage
2s of IBF - 58% damage
45s of normal damage
( 10/60 * 1.16 + 2/60 * 0.58 + 45/60 * 1 ) = 0.963

96.3% overall damage taken.

96.3/66.2 = 1.455

So overall you're looking at a roughly 45% increase in damage taken while kiting compared to not kiting as a Death Knight.

Delete, please, didn't see refresh.

Not kiting is suboptimal from a healing standpoint, but despite the reduction in tank damage, I think the benefits of standing still far outweigh the mana drain on the healers. By keeping him still you are essentially taking one RNG factor of that fight out of the picture by ensuring that the tank can never be marked/crashed and any players who stand in his hitbox cannot be marked/crashed. If the tank gets marked it is almost assuredly a wipe unless you have some people who are very quick on their feet with movement/interrupts.

Sure you can argue that the melee/healers can move with Vezax as he surges towards the tank, but it only takes a minor slip-up to have a mark/crash in the melee pile which is going to take the entire efficiency argument out the window, not to mention its a dps loss for the ranged since there's a good chance that they are missing out on a crash.

I'm not a fan of ignoring certain mechanics of a fight - I'm pretty sure blizzard intended to have the boss kited otherwise they wouldn't have added the 50% snare - but in this case the benefits are pretty clear cut and can be performed with any tank if your healers are smart on cooldown rotations.

They only reduced the damage in 10 man, 25 was untouched.

These are some of my observations from experience and research on vezax hard mode as a disc priest:

Prayer of mending is not triggered by the Profound Darkness aura. Bounces are triggered by the mark of the faceless drain life ability. You're very unlikely to get multiple bounces unless it hops between the main tank and the animus tank.

Spamming shields on the raid from inside a shadow crash to deal with the Profound Darkness aura is very effective and mana efficient. On throughput: glyphed PW:S is ~9-9.5k per cast (absorb+glyph heal). On 25man, assuming you take ~105 seconds to down the animus, the aura deals ~45000 dps to your raid right as the animus dies. Divided by 5 healers, that's a requirement of 9k healing/sec per healer at the peak damage output of the fight, tank and mark damage not included (your avg hp/sec requirement would be lower for the rest of the fight), so PW:S spamming is obviously very competitive throughput with 1 second borrowed time GCDs.

In 10man, beginning at ~60% health left on the animus (30 seconds after it comes out), the darkness aura will be doing enough damage to consume a full PW:S before weakened soul expires, assuming no other mitigation abilities like barkskin. This means once it hits 60%, you can spam PW:S on the whole raid and not worry about wasted or overwriting shields. You should stop shield spamming on non-tanks when the animus is at about 15%, as the aura will stop ticking when the animus dies and not have time to fully consume any non-tank shields cast after that point.

In 25man, based on worldoflogs parses I looked at (we're starting 25man hard for the first time this week, so I don't have my own parses), the aura does more damage and will fully consume PW:S before weakened soul fades as early as 10 seconds after the animus spawns. Additionally, the aura ticks so hard at the end of the phase that you don't have to stop shield spamming until 3 seconds before the animus dies to get fully consumed shields.

For divine hymn, make sure you're sufficiently far from other players that you won't have to cancel it for a mark of the faceless and move, and start it right after a shadow crash hits somewhere else. Make sure you don't get TOO far away though, or you risk creating a shadow crash pool that your dps can't use.

For hymn of hope, make sure you announce to the raid when you're using it, and only use it when several mana users are completely dry. They have to spend the mana before the buff expires or it is lost, and using it earlier is worthless.

This is some good napkin math about the damage taken by the tank. If you are not doing hard mode then this is worth considering. In hard mode, though, I imagine that it is nearly impossible to kite during the animus phase. There is a huge chance of an RNG crash or mark of the faceless. If the animus is moved with general and the DPS all follows, I suspect you are still going to lose a lot of DPS during the movement. And if there's anything I've learned from the past week's attempts--dps on the animus phase is critical and not easy.

Most wipes were was due to lack of DPS on the animus phase letting the DOT stack up too high (60+) with the mob still above 10%. We've identified some areas to improve there, but the answer from the healers was never "I ran out of mana" and always "there's too much damage to heal through". With that in mind, along with the overall intense DPS requirement in the fight, you really shouldn't kite General on hard mode until after the animus is dead (if ever).

I'm sure your strategy works for you. Whether it's necessary or a good idea, however, is another matter.

First of all, casters don't need "protection" from Mark of the Faceless anymore than your healers do. Someone at ranged can be targeted, they have to move. The notion of limiting the people at ranged has been discussed in this thread, but obviously, the more casters you have the less it's done.

Your strategy does change that, but not in a way I'd recommend to my raids. You are moving Vezax frequently; we do it never. This causes a greater chance of a missed interrupt -- especially on 25 mans. It also is movement for movement's sake, which generally buys little good.

If you use the "normal strategy" in your group, your entire ranged dps group is out there, lightly spread, awaiting a shadow crash. Once one comes in, everyone camps the border of it and, well, they need to move less than in your scenario. Yes, once the next one comes, they all have to move, but that's no different than your raid where absolutely everyone has to move. In both cases, all ranged can use the shadow crash. In the "normal strategy", they honestly are likely to be closer to it.

So what of Mark? Well, in both cases people have to make sure they move. Yes, your strategy means it's healers and hunters as opposed to ranged so the dps can continue apace. But then again, the healing rhythm can't.

Since the fight is not really a dps race when performed correctly, I'm not sure what problem you are solving for most groups. Now, hard mode is more of a dps race, but then again, hard mode is a case where moving the boss is even less interesting. By contrast, healing becomes a serious challenge during the Animus phase.

This seems to make sense for 10man depending on the composition of the raid, but if it were 25man, the sheer amount of movement would be much too risky for this to be the best method. If there just so happens to be a moment where one of the range gets too close to the boss or there are not enough people at range, just to name a few things that can go wrong, the tank or people within his hitbox may get crashed and or marked, which would most likely cause a wipe. If anything the most beneficial people to protect from crashes and marks would probably be the tank healers and possibly the range healers if there are sufficient (7 or 8 I believe) people at long range. This way range, who only need to worry about their own hp can concentrate on staying out of damage such as crash and mark, while healers can stay stationary and toss out heals as needed.

The healers are not clumped together but spread out so no one needs to move when marked. On the other hand multiple casters will usually end up in the same crash and a mark on one of the casters WILL heal Vezax. If you restrict crashes to only one caster, most of your ranged DPS will idle.

On the argument about healers having to move on crashes (they don't need to move on marks), only when using a completly stationary strategy is it possible to not have healer movement. However this requires healing through surges which requires more mana than kiting which from a mana efficiency standpoint is bad. I am not saying that moving the boss into crashes is the best strategy, just that there are some merits to it.

Advantages:
1. All casters have access to crashes.
2. Mark does next to no healing and no raid damage.

Disadvantages:
1. One of the healers need to move on crash. Given that usually only one (or two) healers heal the tank at any given time to prevent overhealing it may become an issue if your current tank healer is targeted.
2. Marks on the move can happen if people don't stay in range of the boss.
3. Threat may become an issue if casters have too many crashes. Threat generation will also be reduced by tank movement.
4. Being dependent on close range interrupts (rogue, warrior, dk) may cause problems.

Personally I would say that the argument is reversed depending on whether you're doing the hard mode in normal or heroic. In 10-man, I would still recommend kiting every surge including the one that might happen during the Animus. There should be very little DPS loss if the crashes are positioned correctly to handle it; melee in particular have no excuse for falling out of range of Vezax, as he's snared for most of it and you can run in front of him to maintain your range when he does the final sprint to the tank. Shadow crash on the tank is a risk that will cause DPS loss, but Mark on the tank is ideal because the melee can easily outrange it and noone will be hit.

In 25-man, there are a lot more people in each shadow crash which makes it worthwhile to simplify the fight for them. There are more melee to chase, and more interrupts to worry about. Positioning is likely to get off badly enough to cause problems from movement, and your healers are mostly just bored until the Animus comes out. Plus the DPS requirement is much higher, so a possible wasted crash on the tank is a likely wipe.