Thought about this more and here's what I would do to help people get sets without making it too trivial or caving to the demands of people who just want them to get rid of BoA (fuck that):
1. Fix caches so that difficulty level matters. Their current implementation is still one of the most retarded ideas anyone at Blizzard has ever had. A1 cache - L70 2/4pc set. A2 - L70 2/4/6pc set. A3 - L60 set. A4 - Keeping with the current design, any set item. A5 - Things like set weapons, rings, amulets, offhands. The kind of shit that rolls so poorly that it's useless most of the time, so an extra way to target those particular things would be nice. These drops should be independent of the current cache legendaries, so as to not ruin things for people still searching for RoRG, Pride's Fall, etc. And obviously the set drops should only happen at T1+, and scale accordingly.
2. Add rare purple name spawns to rifts that have the increased drop rates, but ONLY drop set items when they do drop something. Apply a boost to the chance of getting a set item to rift guardians as well, though not to the same degree as the rares.
3. Do something with Kadala. Like, say, add a second shard drop to torment rift guardians that can be used to purchase all the same slots but it gives a set item instead of a legendary when you hit the jackpot. Also, scale shard drops so that torment level matters--this is almost as retarded as the cache design.