SOme people dont sit hours on end waiting for someone to raid.

Maybe...just maybe...Niaz was off exploring somewhere and couldnt get back. Maybe he was badly hurt somewhere, and couldnt get back.
Just because someone doesnt get their butt back to their cabal on...as you describe...one occasion, doesnt really mean anything.

As far as what happened afterwards, well from what it looks like, he returned from where he was, and decided to come try you and the giant. And he died. WHat more do you want from someone?

Sword, flurry spec, villagers, are not easy to fight for anyone. Especially while trying to retrieve, and especially for a necromancer trying to retrieve from...alone.