1.5% life steal won't even cut it on MP4+. You're better off running with a life steal weapon. I personally keep my 2.6% life steal Echoing Fury in my inventory for a quick switch when I come across Reflect-Extra Health packs.
Reflect varies pack to pack, but I think the consensus is that it returns a % of your damage back. There's no way an Inferno-nerfed life steal (even 4.5% max for wizards) can cover that up naturally without some ridiculously high mitigation (armor and resist). It could be fine when hitting one member of an elite pack on lower MP levels, but trust me... it's awfully painful on high MP if you stick with only Blood Magic.
Reflect mobs hit for 10% of the dps you do, mitigated by armor and physical resist. Your 1.5% life steal gains 0.3% of the damage you do as life in inferno. To be able to break even you'd need something like 97% damage reduction from armor and resists. Adding 3% life steal reduces that to a managable 91% break even point.