Hard to call this.
Sage needs abilities to justify being over an Ast/Sch, Ast has Cards and Sch has Chain which are powerful buff tools. All Whm has is Glare, Glare, Glare, and if Sage gets the same treatment as Whm, it's unlikely for it to be over Sch in Optimization runs. It will be popular in the community for being "new", raid wise it's hard to say.
For GNB it's because it syncs with current buff timers including Pld (60 second cooldowns), Drk is an exception certain fights for it's strongest Burst power out of all tanks.