Generally you should switch to LS when you are above 100k dps. Especially since you are going 2hander.
You wont be hitting fast even if its aoe, so its better to depend that huge hit that you get with a 2hander and get as much life back from it as possible. LoH is more for DW/1h+oh that hit faster. Like CMwiz that hit for ~30-50k 1000times/sec.
Im running skorn barb and Lifesteal really helps out alot with both rend and smash. And I think its the same for WD
it mainly depends on what attack skills you will use.. certain skills trigger LoH, and others trigger LS... if you're going acid rain, I believe LoH triggers with that...so theoretically, either would be fine, but you may end up seein better results from the LoH, especially since it can get up to 2k on the skorn alone... of course, the best thing to do is get LoH on other gear, and then a high of LS as you can on the skorn...really, it's preference at this point, but just to be clear, if you're only using the build to farm lower MPs, LoH should work fine
I should add that life after each kill is also a cheap alternative if you farm low-MP. I believe there is no inferno-penalty for life after kill, meaning if your weapon has 4k life after kill, you get 4k hp back, unlike 80% penalty of LS or <1 proc coefficient for loh. The only place where you may have trouble with life after kill on low MP is reflect dmg mobs, which you can use spirit walk for that.
As noted, at very high dps, life steal can do better even in an Acid Rain build. That said, at lower dps, LoH does noticeably better than Life Steal when using Acid Rain and RoT. Even at 130k char sheet dps (actually functionally higher because of Acid Rain helm), LoH Skorn works like a champ for me when doing low MP farming. Something to be said for that given how much cheaper you can buy a LoH Skorn. Be aware though, amp up your damage gear and take that same LoH Skorn into high MPs versus a reflect pack though and ouch, WTB LS Skorn