Help Explain Huge Exp Difference

[jouer2]

Tried researching this, but can't find an explanation. Hoping people here can help.

A friend and I are duoing an Ogre Warrior and a Troll Shaman respectively. We only play together and he is out-leveling me like crazy - like an orange and a half per level at 28.

Based on what I've read on the wiki, Warrior has a 10% exp bonus and Ogre has a 15% penalty so he should be around -5%. My troll should be at -20%. If we're both equal level though, I thought I'd be getting a bigger split of the pie since I would have had to earn more exp to be at the same level. Instead, every level we play he ends up way ahead and it's just getting worse as we get higher level. We were hoping to keep these toons together, but it's becoming a huge chore at this point and I'm thinking of rerolling.

What am I missing here?

Thanks in advance.