plate leather set together with a bow will probably give you more dps in the long run, and you won't even have to use much mp for spells or heals, except for root if you really need to.
you will always find mobs weak to arrows in game, from early game up to high levels(70+).
other monsters also have weaknesses to blunts and rarely daggers too, but those usually have either normal or high p.def, while mobs weak to arrows usually have low p.def.
if you plan to solo a lot, you could also use fighter tattoos, however considering the very low amount of STR human mages have, it would be better to stack on DEX due to better accuracy overall, more attack speed and critical rate.