Added this to weapon enchants. Will be implemented (probably) in 3.1 Don't know how it is vs Mongoose though.

Enchant Weapon - Blood Draining *New* - Permanently enchants your weapon to sometimes grant Blood Reserve when striking an enemy or inflicting damage with bleed attacks. When you fall below 35% health, Blood Reserve restores 1750 to 2250 health. This enchantment requires the wielder is at least level 75.

I'm going to say nearly useless, or rather only rarely and situationally useful. Depending on the rules it procs by, we'll see its effects only in a few situations:

1. Regardless of the presence or absence internal cooldown, it will take some of the edge off of huge hits like dragon breaths that are intended to take us very close to death.
2. Again regardless of the cooldown, on bosses who don't get us below 35% in normal situations, it will slightly increase our resistance to the infrequent but incredibly unfortunate melee-special-parry-melee super hit.
3. If there is no internal cooldown on the healing portion and the proc rate is very high, it will provide a moderate amount of healing in situations where your health is going down gradually and consistently, and you are not receiving any incoming heals from other people to keep your health pool topped off (soloing), but only if its healing is enough to consistently push you back above 35%.
4. If there is no internal coodlown on the healing and it can proc on any hit when you are below 35% (rather than what the wording implies, only proccing on hits that take you from >35% to <35%), it will provide a significant amount of healing in the same situation, regardless of whether it has enough power to effectively nullify all incoming damage.
5. If the healing is applied before the incoming damage, it could save you from a killing blow that takes you from >35% to -2k. This would significantly increase your effective health in fights like Sarth-3D, vs the breaths.

My speculation would be that there is a noticeable internal cooldown, as there was on [Commendation of Kael'thas] for example, and it will most likely proc after damage is taken. If true, only the first two would apply. Since 2k extra healing is relatively small in cases like that, where healers are probably healing and overhealing you quite heavily already, I don't expect this enchant to be useful for tanking.

It's not even situationally useful against Sarth's big breaths. Once Sarth is immune (Shadron's Acolyte) most tanks I know just stop attacking completely, especially when Vesperon's Acolyte/Twilight Torment is also active - no attacks, and no damage = no enchant procs.

At first glance it looks almost completely useless, giving you a practically unnoticeable heal when you're almost dead. But if the Blood Reserve effect stacks, the heal would become very noticeable; a five stack would give you a heal for around ten thousand health, which is hardly unnoticeable. It wouldn't need any kind of internal cooldown to limit it if the heal always consumes all of the Blood Reserve charges, since you'd have an effective cooldown while you build charges back up.

The fact that it procs on striking an enemy and bleeds makes it exceptionally good for druids, since we're the tank that scores the most melee hits with swipe, berserk mangle, and glyphed maul and normally keep a lacerate bleed on the primary target.

To make my theory about how it works a little clearer:

You start off with high health, healers keep you above 35%. Hits and lacerate proc over time, giving you more charges of blood reserve. Immediately if you drop below 35% health, all of the blood reserve charges are spent on a heal.
You then start building up blood reserve from scratch. If you get below 35% again in a short time, you won't have a stack.

something like a stacking effect of maybe 3 or 5 would make it more viable than other tank-like enchants. even then it is a shield effect that on top of savage defense etc. gives the druid a good buffer on larger hits.

I highly doubt it'll stack to more than 2, maybe 3. Having more than 3 stacks pretty much completely trivializes a lot of fights.

I highly doubt it will stack at all, otherwise it would be mentioned.

I am hoping there is no internal cooldown - in that case I would presume that only blows taking you from above 35% to below 35% will proc the heal.

Even if there is a moderate internal cooldown on it, it still seems like a useful enchant. Think of it as an automatic healthstone which can be used many times in one fight.

Obviously if you rarely fall below 35% health it's effect greatly diminishes - in those cases you may opt to have a secondary tanking weapon with a threat oriented enchant.

Let's pretend this new enchant can proc often as Aldhissla describes. Would people drop mongoose or 35 agi for it? I'm not getting why you would unless their is a strong shift to periodic magical damage hitting tanks as opposed to melee hits we would give nearly anything to avoid. Perhaps someone can explain.

Has anyone had a chance to test this on PTR yet so we can stop guessing about it? Would really like to see concrete numbers so we can pick it apart and compare it to our other options. Also possibly make suggestions to blizzard accordingly before it goes live.

Judging by the word 'reserve' makes me really think (hope?) there's multiple charges. To put it on par with that uber new parry enchant, this would have to be 3 charges at least by my napkin math, no?

The wording on Blood Draining seems to imply that it'll proc at any time you're below 35%, not necessarily on hit.

However the wording says "when you fall below", which to me implies moving from one state to another - from above 35% to below 35%. If you were already at say 30% health, and procced the Blood Reserve buff on yourself via an attack, you are then unable to "fall below" 35% health because you already at 30% health. If it functions as you describe then the wording is very confusing, one would expect something more like "Any time you are under 35% health..."

Doesn't appear to be on shard vendor, so I'm guessing its going to be an Ulduar drop.

The way it is worded seems to imply the two portions are separate: Your attacks/bleeds always have a chance to grant Blood Reserve. However, you will only have your HP restored when you transition from above to below 35%.

So when below 35%, you can still get Blood Reserve, but it will not actually heal you until you are healed above 35%, and then fall below for a second (third, etc) time.

I think most of us were aware of that and were moreso questioning whether or not you can have multiple reserves.

I don't understand where this idea of multiple charges is coming from. Is there some nuance of wording that I'm missing in the enchant description?

Two things I believe.

1) "grants Blood Reserve" is bad grammar. This would be different to 'grants a blood reserve', or 'grants an additional blood reserve'. Also, I'm no English scholar, but the word reserve seems odd in singular form. I think I (and many others) have always imagined it to have a chance on hit to grant a reserve, then when hit sub35% it'd expend them all.

2) Secondly, the other enchant that's being released in 3.1 for paladins and warriors (since DK's use runeforging) grants 200 parry rating, stacks 5 times to 1000 parry rating and deals damage. Blood draining was added as a response to druids saying 'well we're still using mongoose from level 70', so most assume that it'd be of similar awesomeness.

In my own humble opinion, I'm unsure why the enchant mentioned in 2) couldn't just be changed to dodge rating and make all 3 enchant-using tank classes happy.

That makes things a bit more clear. The new parry enchant slipped under my radar somehow.

I'm still not sure that it'll stack, though, just because of potential balance problems in non-raid content. I like the idea of changing parry rating to dodge rating on the Blade Ward enchant a lot better.

I think the reason it is written that way, with Blood Reserve capitalised, is because "Blood Reserve" is the name of the buff you receive.

edit: Looks like my assumption about the transition from above to below 35% may be incorrect.
Blood Reserve - Spell - World of Warcraft seems to indicate any damage taken while under 35% will proc the heal.

That's...horrible.

Okay, it's not absolutely horrible. In cases where you are fighting many mobs (or one mob that hits for very little but at a ridiculous pace) it'll be somewhat equivalent to ardent defender, assuming it sticks around. But against most dangerous situations you'll be reduced below 35%, then either barely healed after another near-death blow or more likely killed (then healed for 2k).

Bleh.

I highly doubt I would ever use this +75 stamina enchant on my tanking weap,
or this blood shit, either. More stamina is not worth an almost constant +125 agi and
attack speed increase when AoE tanking, and if I drop below 35% health, either I aggroed too much,
or the healers suck.

I think I saw it there for 10 shards, but didnt buy it yet. Might have been changed in the newest patch.

I thought I might try to clarify what seems to be conflicting information from different posters. The Blood Reserve itself is stackable, starting at around 400 healing received at 1 stack, and stacking 5 times to provide a buffer of around 2000 healing done when taken below 35% health. It also appears that to receive the proc again, you must be taken about the 35% limit and once again taken below it. Of course if this happens in a short period of time, the stacks will not have been built up enough and the healing done will not be as substantial. While this isn't exactly an internal cooldown it prevents the proc from becoming slightly overpowered.

Not the most amazing enchant in the world but at least a step in the right direction, and something a bit more interesting for those hard hitting bosses. Savage defense and Blood Reserve should provide a tasty buffer for some harder hits, but the problem would be if we know the harder hits are coming, we can do nothing to ensure that we crit just before the hit lands - meh..

Would be nice for someone to try it and post back