the problem with doing a percentage based lvl up is, it will lead to abuses lvl 2000 with 8000 stamina and not a point anywhere else
but if they place all stamina they would receive crap xp off boss, you still have to spread out the skill points most of this percents are based on levels which will take others time to get there, this benefits one already up there and been here awhile. Stamina aint nothing if you dont have right att and health either, you need energy, then if you dont have def well you better hide they chain all day. They may look like large percents but for the level tier and what major part has its not really as much as you think
I hope you think for a moment that if you look at the game as a economy, and stamina as currency, throwing more free money out there will only have dire results in the long term.