Well for 1 Fire damage got a buff before chapter 5 was released, at least the mobs did but I think it was overall. 2. Flame has a chance of explosion so they get more damage. Unless you are a Wl/mage you don't get added fire damage I think. So maybe try rolling that if you want the dps. Like the psychic arrows get added fire damage + fire ward gives +% fire damage.
NOTE: Wl/ch -> Energy Influx strike uses 30 rage?? Normally it uses 25 on champ. Is this a error b/c i don't recall seeing it in the tooltips.
The problem you have missed is that as a Wl/C he is keeping up with the mages up until hard mode. If you go into hard mode, then and only then does he drop below the mages he is running with. Mathematically, in normal settings, the mage and warlock should drop at the same static rate roughly, but this is not what he is experiencing. This is due, IMO, to the drop that ONLY warlocks experience in damage, which is really unfair to warlocks. This is kind of how mages felt all through chapter 3, relegated to running non-endgame content to be effective.
Where's Fandie when I need her?!