is kha zix still viable?

He is viable still. I do not like him anymore but people still play him often.

Barely. It takes a good set of runes, masteries and items to make him work now. Full assassin is NOT ADVISED. you dont do assassin damage unless enemies are isolated, which only works when chasing thru jungle and in empty lanes because of that awful isolation range (which really needs to at least be 25% smaller)

I took him as a bruiser top twice, and i was able to outplay a riven and noticeably reduce an enemy nasus's farm. unfortunately, both games ended approx 25 mins in due to surrender so i didnt get to use him in team fights.

His gutting (not nerf, he was downright destroyed as a champ) has made him an unreliable pick. He really only shines when the enemy team is extremely unskilled. He has become like the Ancient Evelynn (some time ago, she was nerfed so many times that she became unusable, and they had to do a full rework)

I suggest taking other bruisers until they fix him. He isnt worth the IP/RP right now.