It is very gear dependent. Right now, I'm stuck on Akarat because I can't do enough damage to take him below 25% (I can take down regular mobs with little or no trouble).
I had exactly the same problem with Akarat until I switched from Clawscratch (TU Blade) to a Sacred Storm Quill (Dagger runeword). That upped my damage considerably and I was able to maneuver Akarat in such a way that I could kill him. Farming for the rune/sacred gear is pretty easy in this build. I found I could reliably farm Tran Athula, K3K, and High Heavens, even if killing some bosses was slow
, thanks to the power of crushing blow.
I also swapped from a Ranger to an Exemplar merc which seemed to really help, although sometimes it seems like my merc is killing everything and I'm just along for the ride