19k in 5seconds is easily outhealable by a pair of paladins. (non crit HL is 5k on a 2second cast so the are slacking/using fol (WIPE CAUSING FOL.... man i hate people using fol on tanks :p)
You should have 6-8healers in the raid
A few pointers
Have 1 or 2 abombs taunted off you by the other tanks. (One healer should be easily able to heal both of these tanks)
Ask your raidleader to assign Druid + Priest Hots + PW;Shield + Earth Sheild on you (it helps a load Hots + Earth shield is ~1500 hps + shield which is 2000+ dmg that you never take.))
I usually have 4healers on me and announce on vent if im stunned.
If you want to avoid knockback entirley , ask the guild to sponsor you some Free action potions, pop one once you have agro, and you wont get knockdown for 25secs, so you'll take stable damage.
when the effects about to run out, yell out for some spammage, and get those big heals landing in time for the stuns.
Our tanks go afk for trash now, heck i sit and watch videos on youtube while hitting consecrate > holy shield. rince n repeat.
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Stats shown are unbuffed as of 28.04.08