I'm not in the beta, but I did do a bit of analysis on Kanj's logs a few pages back, and Umbilicus Eternus was doing anywhere from 6-14% of his total healing, depending on on the encounter. This trait is much, much better than our initial thoughts were. I think going down the middle of the tree (right side), grabbing Unending Thirst, then heading left along the bottom until we get to Umbilicus Eternus is probably the strongest play.
We'll end up with something like this:
http://legion.wowhead.com/artifact-c...ER0BEeARIQFTMB
At which point we then take Blood Feast and then it becomes a bit less clear.
Going down the middle-left would get us to both Unending Thirst and Umbilicus Eternus with three fewer traits, but most of us will take the Red Thirst talent, making Vampiric Fangs on the right side incredibly strong. It's probably worth the short-term tradeoff of needing more artifact power.
By the way, Kanj, if you'll be doing any more raid testing I'd love to take a look at your logs again.