Why is your base xp per kill so low? Higher gems give more xp, I always bomb with the best I can afford. The armor level of your mobs tells me you're bombing, at least in part, with low level gems. Is that so your mana farm doesn't do any killing? But don't the monsters have health so high that they can't?
The base XP per kill is so low because that is wave 6. And I'm only getting 1400 at wave 10-ish by bombing purely by high grades...with maxed skills, and a gem that I can make 3-400 of with my pool(so half pool goes to anger).