I know, my point being is that in order to get the most out of the drain, he has to take exhaustion.
True, but only to an extent. In Max's case, he's only resistant to any B/S/P damage. As we saw from the Wyvern fight, and the possible damage of the scorpions, that damage is the least of their worries. Any elemental/radiant/necrotic damage will blow right through that, and that damage often has more/higher value of dice than on weapons available.
There's a few conditions to that however.
- Berg is/wants to frenzy. Beyond 2 exhaustion it really starts to cut into his ability to hit things.
- He hits with all those attacks.
- The enemy isn't resistant in some way to necrotic.
At level 5, the healing from attacking has a lower min. (3 vs 4) slightly higher average (8 vs 9) and slightly higher max (11 vs 12) than that of CW. However, if any of those conditions aren't fulfilled, then CW is immediately numerically better. Not only that, but CW has the ability to scale, where the only way of Berg getting more dice is critting.
Damage is another story, but then we're talking about a whole different slew of class abilities/spells. One example with more or less the same perimeters exists however - scorching ray. Both the spell and level 5 berg require 3 separate attack rolls. The min/avg/max of that spell, assuming all the rays hit, is 6/24/36, blowing the 3d4 out of the water, even more if you use a 3rd or higher spell slot. Granted both CW/SR require spell slots, but that 3d4 is also dependent on Frenzy.
Point being, the +2(3)d4 is a nice bump, but it's far from outclassing other spells/classes that can do the same thing.