1. for priests.. most of ur skills are affected by the skill lvl + a fraction of ur magic attk. 2. not many parties wld wan to have a priest with mp that depletes ever so quickly.
as for stats, INT will always be ur main one to pump. CON is pretty much a matter of whether u want HP or not. For my character, my con pts = my lvl. u'll need HP to withstand some attacks as there r bosses later in the game that have AOE attks and u're bound to take dmg. if u're dead, the rest of ur team is not much better off either. STR is only required for ur equipment. keep it at the required lvl for ur equips. AGI is a no-no. so that pretty much means u're stuck with only magic equips, ie robes