Another thing about using humans as thugs is the fact that they have too few HPs.
That means that even when geared out, they tend to wear out due to the higher rate of Affliction gain. Even if you play Arco, you'll still have to sideline your human thug quite often.
Also, given their Size of 2, they tend to get Trampled by large units and swarmed by small units
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"Hello, mother. I come bearing a gift. I'll give you a hint. It's in my diaper and it's not a toaster."
- Stewie Griffin
"The artifact which is the source of my power will not be kept on the Mountain of Despair beyond the River of Fire guarded by the Dragons of Eternity. It will be in my safe-deposit box. The same applies to the object which is my one weakness."
- The Top 100 Things I'd Do If I Ever Became An Evil Overlord
http://www.eviloverlord.com/lists/overlord.html
The Brain: Pinky, are you pondering what I'm pondering?
Pinky: I think so, Brain, but then it'd be Snow White and the Seven Samurai...
-Pinky and the Brain
http://www.lolthulhu.com/
-Props to S.R. Krol