i feel like all skills should be unlockable at lv 70, so that when doing low level duty with enough kits, it will make it a bit more fun. lv 71-90 will be just a traits

but there's so much you have to look into like

1. stat
2. potency
3. button bloats
4. lore (job quest)
5. duty support
6. numbers (damage, hp, etc), talking about when they're lowering the numbers in EW for lv 51-90. they have to do it again for lv 1-50