This tier, Blizzard introduced a mechanic to help with Tier gear: the Creation Catalyst.
Previously, the problem with Tier sets was that you could be unlucky and never get Tier to drop for you. Or perhaps worse, you have Tier shoulders, and a higher item-level non-Tier shoulders drop, and you have to choose between the set bonus or discarding the higher level item.
The Creation Catalyst pretty much solves all the issues with Tier. Once a week, you can transform a non-Tier item into the Tier item of the same item level. It's pretty much the equivalent of allowing you to purchase a Tier item of any slot at the rate of one per week.
So the first couple of times you use the Creation Catalyst, it's to finish off your 4-piece set bonus. Then after that, you can start transforming upgrades, always keeping your set bonus.
It even allows solo-players or non-raiders to get their Tier set bonus. You can transform the Zerith Mortis rewards into Tier, so you should get your set bonus in 4 weeks.
All in all, the Creation Catalyst was an excellent mechanic that solves many of the issues with Tier set bonuses. I hope it is carried forward for future content.