I haven't touched Kass in quite sometime on dom and I know he had his ulti nerfed some but is manatank kass still a viable/competitive way to build??

If you don't build tank you won't win as hard.

it 's still an Op lategame build

I wouldn't build him any other way.

The only real choice you have to make in his build is "do I want an early Tear?"

To be fair, an early tear typically puts you behind for most of your midgame too, in comparison to an early catalyst built item / Frozen heart, but it's tankadin that's the ridiculously overpowered build on dominion, yes, and any minor variations should still work out well.