[Edi]

Dom3 has experience and so does CoE3, also implemented very much the same way. Veteran units are a lot better than newbies, but the problem is making them survive long enough. Many classes get tougher summons that benefit proportionally less from XP than the weaker units, but it is there. The problem of survivability is mainly with front line units, but even they will usually get to 1 star if you have a large enough pool. Getting to two stars is a lot more difficult.

As far as alignments, the baron is not some inherently "good" class. He's an ironfisted tyrant when you read the description. Necromancer, Demonologist, High Priestess, Priest King and Bakemono are more directly evil, to say nothing of the High Cultist.

But most of the classes are rather in a gray area.

As far as the environment, some monsters can multiply (like the death mushrooms), but they don't spread over the land uncontrolled. Some events can cause monster spawning etc and with scenarios, it's possible to construct almost anything in that way.