Double the exp gain from Heirlooms and everybody wins.

Simply put, if we increase the exp gain from Heirlooms to 100% everybody ends up getting what they want. The levling will still provide challenge, the heirlooms are optional so if you want you don't have to use them. The people who feel like the levling is too slow now can enjoy a faster pace. Feels like the easiest fix for this in my opinion.