is it gonna be viable? Literally the only build i enjoy.
T16 viable, definitely. Being able to swap about the LoN rings for the LoD gem opens up a bunch of new possibilities. I haven’t pushed GRs with it - Dagger of Darts LoD or Zunimassa’s builds are just too strong to pass up - but I had quite a bit of fun with it in rifts during the season just passed.
You might have already seen it but BigDaddyDen did a video on it prior to season 18. As nothing has changed for WDs between then and now, the build is still viable for 2.6.7/season 19 
https://www.diablofans.com/builds/104775-s18-fire-walker-t16-speeds-2-6-6-lod