How about making this a passive heroism infusion that triggers when your life drops below 0? Give it an internal cooldown like some of the prodigy passives have so it can only trigger so often.
I was thinking a simple Heroism proc that can only happen if you don't have Heroism active. So it can't overlap itself and you only have X turns to get yourself back above 0 health before you die.
The issue with something like this being a sustain is that if it gets deactivated right before you die it can be really frustrating.
I think the self-pin is the most interesting and unique part of it.
If there's a problem with it, in my opinion, it is that its effects don't justify that self-pin.
In history, usually the idea of taking a last stand in a narrow area is for the ability to cut down enemies before they really reach you, as well as the more obvious prevention of mass mobbing. Maybe something like a strong physical damage bonus? 4%*talent level? This, incidentally, would mean it negates Shield Wall's downside at L5, which is pretty cool from a symmetry point of view.
The skill has a fairly long CD, so you would have to think carefully where to use it.