SW does not proc LOH, so using it will never add anything with a SW build, however, it wouldn't be taking away anything either. SW does proc LS but at 45% of weapon damage (with 3 stacks) and only 20% effectiveness in Inferno, you'd be needing to do much higher damage than what you'd be doing in MP3 for it to make a huge difference.
For example if your weapons do 2000 dps then 5% LOH should work out something like this
2000 * .45 * .2 * .05 = 5
Or 2000 weapon damage with 3 stacks of SW, and one enemy would work out to about 9 life regen. That's if the proc coefficient on SW is 1, if it's lower then so is the number (I coudln't find what the proc coefficient was). Also not sure how your offhand weapon figures into the weapon damage calculation. Of course this number should go up if you get swarmed but even with 10 enemies in your SW that's only 90 life regen, if they've trapped you on top of a ground effect, that probably won't save you.