It's a hard dungeon all right, it probably wasn't your fault. AoEs there are REALLY REALLY bad (aka whole room buster of that flesh atronach in the middle, or friggin meteor storm of last boss hitting everywhere).

People running it for the first time generally get hit by AoEs there A LOT, and they hurt, A LOT. Flesh atronach is better off without melee fighters at all, with just tank getting damaged and healed up, as the AoE is too big and too quick to dodge even by rolling away.. Even mid-range players like Pyromancers have hard time not to take damage there.

Last boss (well, duo of bosses) looks even worse, but after learning what's what it's easy not to take any damage at all. Just kill melee boss fast, then burn the stationary caster without getting hit by AoEs he's placing all over the room..

If people are getting hit there, it's probably too much for any (even overleveled) healer to handle. We went there with VR4 healer from our guild and he had a hard time healing there.. mostly because most of the group were melees (tank and dual NB) and half-melees (pyro me)... I ended up standing WAY out, spamming just heavy staff attacks and came closer only AFTER big AoE to apply a DoT or two, just to relieve healer of some pain. Last boss duo was really pathetic though, since we all were there before and avoided all damage.

Your group just have to learn what to hit, when to hit it, where it comes from and don't stand in red and you will mostly be fine till the last boss. I have ran CoH with a non templar healer once and the only trouble we had was on the last boss.

Good to hear. CoH is a terribly easy instance to heal