The general idea behind this build is to use your W ability to use your frostwolf resilience as often as possible. But keep in mind that you have to LAND the W ability to really see any results from this build. With each talent added you gain more and more out of your trait. And the active you pick up at level 7 DOES NOT COUNT from the stacks you build passively. So you essentially have 2 separate heals at work every 30 seconds. Goes a long way towards keeping Thrall alive which in turn also goes a long way towards piling on hero damage. I would say that level 16 is wide open to each individual user. It doesn't effect your healing rate at all so pick whatever you are most comfortable with.

In the end there are 2 things that you must understand when using this build.

1) This build erases a lot of Thralls inconsistencies when used properly...

2) But it still does not change the fact that Thrall is a situational pick at best. Can not carry an entire team using Thrall.