Mmm. For me it felt really unlikely that Mike would do it on his own (apart from Jack helping) that way. From the events in the earlier books he's bonded too tightly to them to just abandon them (ala you can't bed the members of your team). And the abandonment did take me by surprise; you were a little too subtle in your setup... :)
I would feel better about it if the HP aspect was brought in more explicitly so that it's part of Mike's decisionmaking - e.g., the HP convincing Mike it's what's best for the Keldara in the long term, not Mike just escaping the burden of being a danger for people he loves (which is how it came across to me). But far be it for us to dictate your story to you.
Looking forward to Gone a-Viking!