I use to wish that past lives would give a stacking 5-10% stacking bonus exp so that future TR's would be faster, and this would accomplish something similar.
As for adjusting the TR exp curves, if you make it a base % increase that is equal among all levels, then you make TRing much more pleasant. 1.5x for a first TR, 2.5x for every other would be pretty reasonable without cutting much of the total exp. Even making it so you end up needing exactly the same exp total to hit 20 as now would still be much better as long as it is a static increase for every level rather than an exponential curve. Sure you don't get to higher levels as fast, but you move lots of exp to the lower levels and away from quest-poor levels (or levels where there are enough quests, but where the exp/min is atrociously low like in shavarath and the house cannith quests).