According to the instruction manual, every character class should be able to level up to level 5, gaining a new Unique power each level. For some reason (specifically in skirmish games) I can't level any character past level 2, with the exception of my Clerics, which I can get to level 3. I don't think this is an issue that can be fixed with a patch, but I could be wrong. Am I doing something wrong? I keep playing and fighting the re-spawning monsters to gain truckloads of experience, but no characters can level up past 2.

Any help here would be appreciated.

Isn't there any level cap in that scenario?

Not according to the manual, no.

I have never had any such problems. I assume that you have built multiple copies of the same building in the same building 4-pod?