I cant claim to be an expert, but I had a lot of fun playing an Aasimar Evocation DC Cleric on mid reapers. I have a few past lives and I have maxed all the epic destinies, but I don't have any completionists - I still got my DC upto about 110 or so and Cometfall, Burst of Glacial Wrath and Implosion were all very effective. (Yeah, I was surprised cometfall was still working)

My primary role in my group was healer, but I was still able to solo top level reaper 1 content with my robot hireling. Burst of glacial wrath is a very effective opener, arcane tempest gave me some DPS and implosion worked against anything not specifically immune. (Long cooldown, but no spell resist)

Oh, and I'm sure everyone knows that at high level turn undead is just not worthwhile...