I don't know anything about staves, never used one.
The incarnate can deal physical or magical damage, depending on the surface you raise it from. It is strong but not as strong as a normal char (luckily). My incarnate on level 20 with 16 points in Summoning deals about 800 to 900 damage or so with a normal hit. My lvl 20 twohanded warrior with lvl 16 to lvl 19 gear deals about 1700, my ranger 1400 damage with a normal hit. They have 98% and 83% crit chance. I think that could be better with better gear, but you can see the relation.
A "Cleric" in the sense of the game is a Necromancer/Hydrosophist combi. It deals not that much damage as long as the physical armor is not gone. It can deal a lot damage with Decaying Touch + heal, but you need to remove physical armor first. The main task in all fights is to remove the armor asap, and both incarnate or onehanded warrior or Necromancer are not the best at this.
