i am gonna sit on 5mil i think for it, cos stamina leech and swing speed means low dex ideally, to use it properly (or a slower wep).
regardless tho, magic arrow will still interrupt spells and add as much damage as like 50% DI (about 5). the good part is you will not slow at all while you are using this wep, but the bad part is that bonus will only come into play while your stamina is low, and that wont be for long because of the leech, so while it covers a problem, the problem is only gonna be there on the odd swing.
that said. this would work on a lower dex, higher int build. you could literally just get a full mana bar, run in and spam like 4-5 AI attacks in a row. you'd then have to back off to regen mana, but that tactic would actually be more effective for straight out killing people.
thinking about it, if you paired that with full med suit, budget in meditation, you'd have nice mana regen...