I just grabbed the RAIN for Unity 5 version off the asset store (it is the default version that loads if you import from within Unity 5) and the standard DarknessWarlord character off the asset store. I do get a couple of warnings about IK in the console (we’ll track those down) but otherwise everything seems to be playing fine.
I was using:
Unity 5 RC3
Sentio Darkness Warlord 1.0.1
RAIN 2.1.10 for Unity 5