First, what level are you? At 70 lifestealing isn't a viable enchant EVEN for melee classes since it starts to get gimped at 60.
Secondly, even spamming wingclip is not gonna be proccing this enchant like crazy. A rogue DW lifestealing still averages the proc to around 6 ppm and they have a 1 sec GCD on most of there abilities instead of a 1.5 sec GCD on wingclip.
Thirdly, the heal is ONLY 30 hp (at 70 it is only 20). Even if that is proccing once every second it won't be saving you from dying (And with 6 PPM it'll be proccing once every 10 seconds).