The exp requirement after 300 is too much of a jump. My solution is to break it down into 25 level chunks. So 300-333 would require 200k exp, 333-366 would require 300k, then 366-400 would go to 400k. Then everything after 400 would require 500k-600k, then what you already have post 500. This way most players over 400 would balance out, roughly, then it will ease the brutal leveling from harbinger tier to be able to hatch vanguard tier dragons. This should be applied retroactively to not anger higher end players, if they actually care about levels after a certain point.
Ah the ol’ 333-300 = 25 equation, i remember it well!
Anywho, it’s been suggested multiple times before, including variations on your suggestion above. Maybe tag that post instead
This same post subject exists here: Insane XP required to level after 300