I'm currently getting achieves done, I'm doing them in sections, right now I'm trying to get ALL pet battle achievements done for example.
Leveling what is practically a "perfect" team for the Celestial Tournament is possibly one of the biggest time investment's I've ever done in WoW, and I've done Bloodsail, Winterspring, Furbolgs etc back when it was a pain in the arse, raided server first, etc, but this takes the cake a bit.
It's annoying at times, and I had zero interest in pet battles before I started, I'd recommend it as an excellent time sink if you are looking for one.
Another is getting all the rep, titles and mounts from the Argent Tournament if you still haven't done that.
Of course Gold Endless 30 and Brawlers Guild Rank 10 + Collect Your Deck is another investment
I'm also grinding dungeons now and again for any missing Heirlooms so I have full sets of everything.
Done CM's and look to maybe go for realm time soon, also run Flex every week for heirlooms too and levelling a lock, dk and priest.
Alongside progressing on Garrosh 25H, I'm pretty damn busy....
Oh and the 200 mount achievement.