From what I can tell, last stand kicks in on wimpy, or when a skill actively prevents you from what would have otherwise been a successful flee (cutoff, parting block, entwine, pounce?).

In the case of the majority of the above skills, these also lag you when you attempt to flee. However, since entwine doesn't, it's very possible to get a massive number of hits in on anyone who entwines an orc.

Of course, I'll be perfectly happy if you say it's a risk of entwining people, but it did seem a bit overboard.