I'm not sure how it works now but I suppose you get 3 percent bonus/genaration but there is also some limit to max xp gain?
If so I suggest at lower gens the bonus to be higher (like 15 percents for gen 1) and on higher gens close to the xp limit to be lower (like 1 percent for gen) - the numbers don't matter, i sucked them up from my arse, only the basic principle matters. This way casual players would get some nice bonus for their 1st gen while grinders wouldn't loose anything as the average ammount of xp/gen would stay almost the same.
What say you?