Was something broken because of this? Something out in the world or?
My main concern is Timewalking. Using old sets in TW made it enjoyable. Old sets certainly are no more broken than the active sets (MoP and WoD) will be, so it can't be that. I've seen current raiders keep up with me and surpass on all the toons I've created min/max TW sets for, even when I'm using old legendaries.
Creating the TW sets was 90% of the fun of TW for me. Its obviously just a novelty difficulty, not meant to be a real test of skill. The most challenge you get out of it is a few obnoxious mob packs (I'm looking at the hill past Ick in Pit of Saron). So it can't be that old set bonuses trivialize TW, they don't trivialize it anymore than current sets do, and its a trivial difficulty anyway. So surely the change can't be due to old sets in TW.
I can't figure out why they would make this change. Hopefully legendary procs still work, and old gear still has the gem slots, but man farming and mix and matching the set bonuses was the funnest part.

