every spec was viable for something
and every class was viable for everything.
people seem to be confusing vanilla with legion.
1. in vanilla you didnt just "raid or die" you could actually do other stuff
2. specs were much more specific and had more identity it wasnt "everything should do everything" like it is now.
3. if you wanted one thing with your class you played that spec, if you wanted another you played another.
ideally they would cycle from 1.0 to 1.12 and when it runs its course they could do new stuff (and balance changes) in 1.13 if they wanted.