Also, in my experience Kalecgos (the human) seems to take more damage when the dragon enters enrage. Normally he drops fairly slowly, but last week we had a period where I was in the shadow phase with no healers, so I just watched Sathrovarr beat Kalecgos while I waited for reinforcements. He dropped from 40% down to about 10% in 10-15 seconds, then dps came in and beat Sath down to his banish point right as I taunted.
That's just my observation from one or two pulls; it may not be accurate. But if he's always taking that much damage, then I really don't see how you'll be able to run with two tanks. Even the 10-20 second layover while the next tank is waiting for a portal to spawn is going to be enough for Kalecgos to die at that rate. Since the fight is hardly a damage race, substituting a dps class out for a third or fourth tank is an extremely small sacrifice. I don't see four tanks as necesary by any means, but we did try running with four our first couple pulls and it gave us a fallback in case someone died. Ultimately I'm not sure if it really mattered either way since you can shortchange damage output on the fight more or less with little or no consequence.
-Splug
_________________
(Usually) Prot warrior:
http://www.wowarmory.com/character-sheet.xml?r=Illidan&n=Splug