My apologies if this has been addressed already in another thread; I DID spend a good half hour sifting through the Advanced Search for "Hydross" and "Druid" but all I could find was discussion of resist gear, not aggro generation. So anyway...

My guild is working on Hydross now, and with our current setup we have myself (feral, obviously) and a warrior assigned to tank the adds. We both have decent hybrid resist gear so that's not what I'm concerned about. My problem is grabbing and holding more than one add on me reliably.

We've tried a couple different strats, one where the warlocks rank 1 banish 2 adds, and the warrior and I each grab one of the remaining, and focus fire them down in time to grab the banishes as they come up. This works fine as far as maintaining control, but the DPS is too slow, so we're looking into AoEing the adds instead. My problem is, I can taunt one, charge another and swipe, but by this time the other two are off running in separate directions after the DPS, and I spend the rest of the transition chasing stuff futilely because I can't get close enough to hit it and regain any ground on threat. Yes, my warrior partner is helping, but I feel like I'm not pulling my weight on my part of the job and would like some advice on how to improve.

Do I need to swap out some of my resist gear for +hit and such? Is there some pattern to taunt/mangle/bash/swipe that works better for holding four mobs (or at least two of them)? What are the successful druid add tanks out there doing?

I posted this question on the WoW druid forum and so far the only answer I've gotten there is that you need four offtanks in order to do the AoE strat. Which really seems excessive to me: there has to be a better way...

If the adds are going after the dps just have them dps hold off or dps hydross until you have stable aggro on the adds.
2 tanks is plenty for an aoe strat as long as you give them time.

Don't go overboard on resist as an add tank, especially if you are trying to keep two of them. I wear both the crafted rings and then enough green/blue resist gear to get me to just above 100 unbuffed in both schools (plus uncrittable from +def obviously).

Having said this, you don't need masses of tanks to get the AoE strategy to work - or at least a hybrid strategy which we use.
We always banish a single add. Myself and another Feral Druid/Warrior pick up one each, if there's a spare Warrior in the raid he picks up the 3rd, if not the released Hydross tank grabs it. They are all clustered below Hydross and the melee focus fire the first add - after that its on the boss and AoE. With a downranked Banish, by the time the first add is dead its tank has just enough time to find it and taunt/mangle to bring it into the aoe mayhem occurring under Hydross. Using this we usually get 1 mark duration of full damage on Hydross minimum even if adds break loose before its time to rinse and repeat.

We Rank 1 banish one add, Rank 2 banish a second, and have a protection paladin and feral druid each pick up one designated add.

Ranged is told to assist the druid, who seems to be able to pick his add up cleaner, and they burn that one down in about 10-15 seconds. DPS switches to the second add, and done properly, both are down before even the first banish is up.

The druid picks up the Rank 1 banish, the paladin the Rank 2, and they bring them both on top of the boss (in poison) or spread out (in frost). In poison, melee assists by using AE abilities -- SS, Cleave, WW, BF, etc., and they die quite quickly.

We typically have 25+ seconds of pure all-out raid dps on the adds during poison (we switch one second before 250%), and the melee is on him from the start, as soon as the tank picks him up. During frost, the ranged gets 5-10 seconds to do some dps, but melee usually churns 4-5% of his life off during this phase (we switch at 100%, for safety).

This strat is most definitely slower than the AE strat: our best kill to date was 9:25. However, it's very "safe" -- with only two adds, and with two banishes, there's a lot more focus in terms of what you are killing, and if your tanks are competent, they only have to pick up one add at a time.

If you use this strat, I suggest promoting the warlocks so they can give their banish a unique raid marker, and then count down the banish timer for their tank -- our lock goes "<druid> : coming out in 3 2 1", so the druid can time his first hit effectively.

Our druid runs about 250/250 buffed NR/FR, and is very resistant to the hits -- he doesn't take big spikes at all. Our pally runs mostly unbuffed, and spikes a lot more, but doesn't really have to worry about gear. /shrug

Edit: our raid balance is wonky compared to most -- 2 prot warriors, 1 arms/fury warrior, 1 full fury warrior, 1 protection paladin, and 1 feral druid. For Hydross, the two dps warriors do just that -- dps.

When our strat called for me to hold 2 adds i found the most success with, mangle->bash first add then feral charge lacerate spam 2nd add, then taunt after charge effect wears (or thereabouts) and head back to your first add and proceed to multi target tank. This works best if you hold off AoE for at least 7-15 seconds first.

That being said, this is not easy to do and really just adds way too much randomness and probability to wipe with misses/parries/dodges etc. its difficult enough to carry through 1 transition much less multiple transitions in a row. We found more success with a rank1 banish on 1 add, 2nd OT on 1 add, MT who is currently in off phase on another, and then of course you. Just pick up the banish before it gets out of control.

Now, THAT being said, just roll with 3 OT's, 2 MT's, and tank all the adds and let your AoE go crazy. It really is the easiest way. The other methods are really only for raid compositions where you dont have the people to do it with 1 tank per add.

Regardless of the strategy you use, a Piercing Howl dropped on the adds when they spawn never hurts.

Crowd control is key, as it is in every other multi-mob encounter. Priercing howl, slow traps, frost nova, pala stun...whatever you like.
Asign persons to each Add spawning around Hydross. For the AE strategy you need 1 tank for each add to make everything work properly. If you only have 2 Offtanks+one Phase tank that has nothing to do you should banish one add. Bring 5 tanks and you will be perfect. You do not need any resistance for the offtanks, just assign one healer each for every tank. The current maintank don't get so much damage since the mark is very low.
The problem with one tank holding two adds is that if it is not stunned when it comes out it will mostly eat one dps or healer so asign paladins to adds that cannot be tanked right from the start. So you can grab your first add and then take control of the seconds one. But tanking two adds against casters going all out AoE after 5 seconds can be very hard.

We seem to do it slightly differently from the older strats. We use 3 OT's, 1 usually a warrior in mixed resistance gear, other 2 usually Druids with relatively minor resistance gear. Warrior grabs 2 adds, Druids 1 each. DPS down one of the warriors adds while tanking the other 3 close to hydross, after the first adds down all dps goes back onto Hydross and we Seed of Corruption spam the remaining adds down.

Aggro on Hydross is never a problem as we get the few seconds time it takes to kill the add to re-establish aggro on Hydross before DPS starts going all out again and the Druids/Warriors have plenty of control over the adds.

We banish one, tank 3 (2 by the two designated add tanks in mixed resistance gear and one by whichever Hydross tank isn't currently tanking). The most important part in controlling the adds is slowing them when they first spawn - frost nova is great for this, but frost trap and piercing howl all work equally as well. We have a warlock banish the back add and the other three are picked up by the tanks. Warlock start Seed of Corruption spam immediately and we AoE them down on top of Hydross. Melee use Blade Flurry, Cleave etc. When the remaining add comes out of banish we quickly focus it down. This usually leaves us over 30 seconds on Hydross in each phase which is ample time to kill him.

Piercing Howl in general is actually what you're best off relying on. It's kind of hard to Frost Nova or Frost Trap Frost immune adds, and while it does obviously work on the Nature adds, that's only one half of the adds you'll fight.

Nailed this one on the head. There's no reason for you to have to get more than 2 of the adds if you have a 2nd tank working with you on them. We have 2 bears wrangling adds, they each grab two. The mages and locks hold their aoe for a few seconds so the bears can get maybe 4-5 seconds of threat-gen time. Rotating frost novas on the nature adds works wonders while blast wave/piercing howl/earthbind work wonders on the frost adds