RoE... what does it do? (exactly) (in General)

I have been testing the use of the RoE on my small character Miho... and i haven't noticed a difference in the exp i have been getting... im sure that it does something nice, but i am unclear as to what...

Basically it helps you turn your low xp minion into a better minion. You won't see much difference in 1 char set, unless you look over a long period of time. It would be interesting to see the difference, but for that you'll have to either keep really good tabs yourself or push for a calc like I'm doing..lol.

If I/m not wrong, a RoE will help to increase your exp by about 20% for a one minion team. And more if you have more minions.