The WW build is very sensitive to lag and gets worse with lower EHP. Your EHP and leech seem fine, so I am guessing you are just getting a lot of lag when you play. Lag is a reason to turn on all numbers -- not just heals. You can see when you are hitting stuff with numbers on, as they will suddenly stop during lag storms.
To fix your problem, I recommend doing this --
1) Hit "V" to show all monster health bars. If the bars aren't going down when you think they should, it's lag. This may be less obnoxious than 2).
2) Turn on all damage numbers or at least white hits or criticals. It will make lag easier to detect.
3) Incorporate rend into your WW build. Substitute Rend:Blood Lust for warcry:Impunity. You may also be able to drop bloodthirst for superstition when you do this.
Rend:blood lust is a great skill for keeping you alive in bouts of lag. When I see lag, I start mashing rend to tag as many monsters as I can during the intermittent communication. Even if you think you are clear of the pack, you should do this. The server thinks you are somewhere else, surrounded. You tell the server to rend, and if you are surrounded on the server side, you will hit things.
What you do now most likely is cast sprint and run away from the lag. You think you can keep running, but actually, you are stuck in the pack. You collide into the monsters and cannot move. Even if you WW, it doesn't help. The server sees you clicking on a strange location -- it is too far away or in some void, so it doesn't let you move. You stand still channeling WW or sprinting in place.
Typically with rend up on a few targets, you will be unkillable. Rend persists for 5 seconds and it doesn't matter if you are lagging or not -- the heals will still come in. With rend in your build, you will spend less time punching your monitor when your ISP craps out.
This does not work as well for a dual wield barb because rend is not as good, but for 2H WW, it works great (one reason to not be dual wield/WW)!
There is a separate issue with dual wield WW where leech seems to stop working, or seems sluggish. This can be lag also, but sometimes it has to do with the weapon speed being referenced at that moment in time. If you get the slow weapon, your ticks go down and your LoH and lifesteal both plummet until the next weapon is swung. You will see fluctuations in heals coming in - against difficult elites at high MP, you may be just barely winning at the start, then the slow weapon turns on, your effective dps reduces to ~70-80%, and your health drains out, and you die. If your weapon speeds match (or you have just one weapon) you will not experience this phenomenon.