The real issue is whether or not you can use them effectively.

You can use Corpse Men effectively, but it's more costly than it's worth.

I have yet to play in a game where someone uses their Air Gem Income, with an Staff of Storms (or Lightning Rod) and start summoning Corpse Men.

The same can be said for Hama Dryads. I have never summoned them for their cost effectiveness or their special abilities; but on a lark.

Both of those units could use a slight change or adjustment in either +Path bonuses to make them more attractive to even use them situationally.