This instance appears to have gotten stupidly difficult (ie impossible).
The amout of damage the troll is now doing in T2 Challenge is bascially a guaranteed wipe. Without spoiling, the "old" tactic no longer works, and it needs a different approach.
I have no problem with that, since it makes it more interesting. What I DO have a problem with is the fact that a L75, non-scaling instance, offering 1% rewards to a level 85, is virtually impossible in T2 challenge. We ran with an 85 Guard, an 85 Minstrel and an 81 Ministrel. The best we could manage in about 8 wipes was four pillars down but wiping before the sun got the troll.
Unless this instance is actually invisibly scaling, there is no prospect whatsoever of completing T2 challenge on level, and I don't care how good a group we are talking about.
So come on Turbine. Making an instance difficult by simply giving the boss lots more morale and/or lots more DPS is just lazy, lazy, lazy design. Either throttle back the damage to a point where it is do-able, or genuinely scale it, with all the implications that has for rewards at L85. Otherwise, this is just another once-great instance consigned to the graveyard. And that particular graveyard is starting to look rather full.