Is there really any point to the increased XP for leveling further lives? Especially given that you still have a massive grind of what 72 Class lives (including the archetypes, and including the Dragon Disciple which isn't released yet), and 48 racial past lives (including the Dhampir from Lamordia). Iconics and Epics as well, though they can double up with Heroic lives or Racial (for Epic). 120 lives, plus 54 Epic lives and 30 Iconics (probably 33, as I expect a Dhampir Iconic with the Lamordia expansion). Even if you kept it at the 1.9m XP that is 228,000,000 XP to grind through for Racial and Heroic triple completionist. Another 445,500,000 for your Epic completionist on top of that
Average it out to the Second/Fifth life XP curve for all lives and be done with it. Keep it simple, don't over complicate things. I get the goal is to keep players engaged and playing, but at this point, the grind is a turn off for even long term players, not to mention new players.
Not to mention once you're on the TR grind, you tend to build a leveling list and never hit content outside that list. XP/min becomes the game, which negates the value of a lot of fun content that is poor XP. A lesser XP curve will let players pick through lesser run content just because it's not as important to maximize the XP gains per minute. That will drive engagement and keep players playing, as they're not getting burned out on the same content life after life.
Which comes to Epic; most of the Epic levels are severely short on content, while you have an absolute glut in Legendary. There's enough Legendary L31-32 content to run to cap three times over by itself, with L32 having the most content at 77 total quests and raids. 34 is next most packed at 42. 31 has 29. From 30-35 is 191 quests. 20-29 is 111, with the bulk being at 21-24. Only 34 quests at 25-29. Outside of Borderlands most of it also lacks any viable gear, with EGH stuff being comparable to EBL stuff. The lack of viable content and loot make Epic even more of a grind than Heroic.