About the Dance of Death / Deathblow interaction: I've noticed on more than just deathblow's, I'm not getting 50 stamina back. If the passive is just supposed to trigger on your active character's explicit last hits and not anyone in the party, then this might be the cause.
Also deathblow will routinely drain 100% of my stamina on use, which coupled with the fact that I don't get any back from Dance of Death, is a giant pile of ****.
It will consume 50 stamina with the first hit, and then the second hit will trigger and the rest of my stamina is drained.
I've done all this testing with Cole/Sera as I was looking to making a DW Rogue for my nightmare playthrough, but in their current state I don't think I could stomach it.
Edit: Thank you lastpawn for making this thread in the first place, I was heading over here to figure out where I could report the deathblow stuff and was pleasantly surprised someone had already made a post.