Pretty sure Paletress's holy fire does fire damage, I drop a FireResist totem in my farm and it negates more damage. I farmed the heck out of the place on normal and hero... still missing one haste trink and one 1h SpellPower weapon on my shammy team Pretty much got and de'd most everything else multiple times. I find if I run the instance during peak server load I have a much tougher time than off peak times. Lag seems to effect this instance more than others.

However, I have not gone in ToC in a while, ever since I subbed in my hunter for weeks trying to get the polearm to drop and hate the place with a passion now (the pole arm dropped the one day ToC was the daily and I decided not to take my hunter). Besides I think when 3.3 hits most people will be skipping ToC all together. Of course with the removal of daily heroic quests and the introduction of the daily random badge reward, who knows how many times we will be getting stuck in ToC. Unfortunately I have two more teams I a leveling up and fear I will be back in ToC a bit more...