Which Orc hero do you prefer?

Kragg is simply not suitable for late-game; Invocation is better there, but in mid-game or for rushing, you can enhance his ability.

I agree. But still. Mine was level 21 and took down 2 or 3 Paladins. In general, that's not that many.
With double strike, he'll take down about 5-6. That's definitely much better.
But still, it's not excellent.