Playing as the Sylvan faction (Disciples 2).

I always take the Knight.

Hmm. In the last scenario of the campaign for the Elves, I was given a Knight, and I leveled up two Barbarians. So, the Knight wasn't very eager to outpace them. Rather, the Barbarians quickly caught up and even surpassed him in damage. However, after each battle, there was plenty of experience – enough to level up the hero.

two Ice Golems

And why not Fire Golems? Or are you afraid of running into a Dragon?