I tried this adventure two days ago, on hard. I'm a level 5 favored soul, a bit low perhaps. the rest of the party consisted of 2 warriors, a paladin, rogue and sorcerer, level 6-8.
We got massacred by the mages. Either they disabled one through hypnotism (I was unaffected due to my high saves) or they one-shot you using a 98 damage frost spell. Rediculous, 98 damage in a level 5 hard adventure? I pimped my hp using toughness and racial and class toughness boosts and barely make it over 100 (102 iirc). I'm quite new now, but do I have 300 hp in 2 levels to survive this kind of punishment? suffice to say, we didn't get far. I'm starting to see this in other hard instances as well. the 'normal' difficulty is a breeze. I even have to hardly throw out heals nor buffs and we breeze through, but set it to hard and it becomes a slaughterfest of one shot kills and control spells that completely disable characters.
Am I doing something wrong? Is hard meant for +5 levels or something? What about elite? Level 20 only from level 5 and on? I did waterworks on elite without a problem on level 4.