I was reading about [some builds][1] on the official PoE forums and I noticed that a criteria is

>Atz: Atziri Viable

>U-Atz: Uber Atziri viable

>U-Lab: Uber Lab viable

I am familiar with what "Atziri/Uber Atziri" refer to (and I suppose that "Uber Lab" is just another map).

My question is: are there objective criteria to decide if a build is viable or not for those maps?

If yes, what are these? 

  [1]: http://www.pathofexile.com/forum/view-thread/1713810