Ok so heirlooms are hard to get right and only mains get to trade.....
I'm gen 12 and my suggestion would not help me as I already gain +33% xp, so here it goes............
All mains start with a +50% xp rate gain, like an generation bonus I get at +33%, the "Main" rate gain dissapears if u hit lv 31(so 31-35 is still long ass hell), each gen you gain it goes down by 5%, while u still gain the 3% for the generation, so at gen 11 you still get +30% with +3%(each additional generation afterwards)
I think a problem in the game is balancing the game for new players so they want to stay, I know my teenage cousin quit because of the grind(at the time he also said it was a "rangefest"), also all the high gen characters(like myself), would not benefit from this at all so it's a true win for the little guy