I haven't seen anything about the fact that the stat bonuses are based on... well, base stats (that sounds dull). Which means that with 250 base INT, no matter how much total INT you have, the 5% bonus from a character card will be 13 INT, and thus something like 40 MATK, along with some mana and MDEF.
The real problem here not being the fact that the 5% are calculated using base stats ; rather that Intelligence in this game has little to no use what so ever, given a good weapon's attack bonus will outweigh any other equipement's offensive stats as long as PvE is concerned (critical damage and rate excepted of course since they scale on said attack).
As for your ranking, Agitodesu, I'd say Agi isn't useful since Magicians have very little of it without equipment, which is what this 5% is calculated from. 5~7 Agi on a character card doesn't sound too useful to me... Same thing with Health although its efficiency increases with character's level.
Max HP, on the other hand, has more use since Monks have plenty of heals based on their own HP (Slow heal, Instant heal, this... thing with a nurse which name I can't remember). Having a fair amount of max HP is a way to avoid spending much money into Defense and enchanting gear other than your weapon, since you can heal yourself (note : and your party members) extremely well. 10% max HP can indeed be a 7~8% increase on the effectiveness of these heals, and an average higher survivability / lesser need to use mana to heal / happy party members etc.
Other things I'm pretty much okay with, although my personnal preferences would lead me to ranking Hlt higher than Int... Movespeed still is the top-stat to get.