Assuming that sebasold's assumptions hold true, then for a base damage of <500, full INT (or STR for fighters) gives the greatest damage (over an infinitely large number of attacks); in the range of 550~1150, the mix of 25 SPR and the rest INT gives the greatest damage; and > 1200 full SPR gives the greatest damage output.
At level 52, with my most powerful spells, hits on yellow mobs don't go above 500 =/ On those dark red things, not above 350. I've convinced myself that the 25 points I put into SPR is only useful at killing low level stuff. Oh wait, that can't be useful at all...
