There is a post somewhere with all the class and race experience modifiers, but I do not think that is the issue here. Both necros and enchanters have a 10% xp penalty, so that shouldn't be the problem unless it is a bug. One thing that you need to be aware of is the way xp works with pets. I'd suggest necroing one of those threads. They are somewhere in server chat. You can also look at old patch notes to see how the mechanics work.
It might not seem like a big deal, but if you can replicate a bug, you should def post about it in the bug section on the forums.
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