I'll also add in this little fact :
Player retiring at lv31 played half his time under lv30.
Player retiring at lv32 played half his time at lv31.
Player retiring at lv33 played half his time at lv32.
Etc...
So actually, you gain to stay at a "good" build when retiring at higher levels. So it's already decent enough.
This heirloom reward is fine as it is.