Experience seems to be a problem. It just seems to be too low for all the monsters.
Yes, most definitely.
Pretty much any enemy, no matter how difficult they actually are to face, will generally only give 1 XP, with a rare chance of 2 XP if they happen to be Blue-Labelled enemies.
Orange enemies can give 3-5 XP, but are obviously more difficult.
I'm not sure on Red Enemies, since I've only defeated one with the help of a wandering adventurer (which was really lucky, seeing as how most other times Red Enemies will just destroy whole parties of wanderers).
And if a Blue Boss only gave 10 XP, it's a bit rubbish.
Either enemies need to provide more XP, or the XP requirement for levelling up needs to be reduced.