Actually from my own testing to, I agree for the INT part, it seems to do nothing, even with drastic increases, as for PIE that does make a difference. PIE increases mp siphon amount, accuracy, and also magic resistance(chance to get hit by 0)
As for MND, that just effects mp(like you all know im sure) and healing amount. So if you only play melee my main concern would just be PIE and MND for now.