The most USELESS monster.

The most useless minotaurs

O_O Minotaurs?? That's quite a statement...
Don't you think their block ability is pretty cool? Minotaurs are a good defensive unit, a bit random, but if luck is on your side, you can even turn the tide in battles that seemed lost. And as a defensive unit, minotaurs are unmatched.
By the way, Medusas don't have high attack power, although petrification sometimes compensates for that. And their infinite supply of arrows can also be a game-changer.

As for Ogres, they just weren't lucky. In Whirlwinds, they were weak and slow. In the expansion, they were improved, and they became useful, but Cyclops are still Cyclops. Area-of-effect attacks are definitely powerful. Although, I sometimes used Ogres when I didn't need level 3 units later on, because of their magic. 2-4 Ogres provide good support for heroes, and Thunderbirds are very strong under Serpent's Blessing.