Help! I'm playing against human players with mages, and my hero is Orac, while theirs is Laslo.

Yes, everyone can overwhelm mages at the beginning... you just need to level up skillfully!
1. No Engineers! This class won't work against mages! Goblins will defeat them...
2. Maximize magic resistance; they don't have any overwhelming magic, which is a big disadvantage, by the way. Of course, there's the Staff of Jesus, but it's not guaranteed to appear in the shop.
3. Try to rush the mage so that he doesn't cast any spells.
4. If you drag out the game, you might encounter problems.
This is just a general overview...