It's a pity, they should have tied reinforcements to Blood, not Tears. After all, it's not healing, but overwhelming the enemy with numbers. Otherwise, the logic of tying Draining to Blood is unclear...
Regarding tactics.
The Sadists and Fiends are just beasts. Especially the Fiends. Someone wrote (I'm too lazy to look) that it's not necessary to upgrade to Fiends, because they don't deal full area damage, but only 25% of their total damage. That's not true. It's additional damage. In total, 125% to everyone without retaliation. Plus their bonus, plus under Draining... As a result, most battles are won only with them. Reinforcement - run to the enemy - the enemy surrounds and takes a beating. After level 15, you can probably do without reinforcement :)
The Dogs are also good, but there are few of them, and they die quickly. I only take them with me for particularly difficult battles. In the fifth game, they were a lifesaver due to their retaliation (almost like ranged attacks), but here, retaliation is sorely lacking.
Is the Frenzy skill bugged? According to the description, it should last for 1 turn, but it accumulates. Well, of course, it's fun to beat up some weak stack in a long battle... plus 2 damage to yourself, minus 2 damage to the enemy per turn :) I wonder if they will fix it? It doesn't seem to create a significant imbalance even with this implementation.
Liliths with magic damage, I think, ruin the Multiplayer experience for the Inferno Warrior :( Dog retaliation would solve the problem...
I haven't tried Destroyers, Broodmothers, and Demons yet.