Looking good so far. Tried on a couple different toons and it seems to be working correctly.
Haven’t been able to find anything else I’d instantly see as a bug or issue with the new system in general. Soo… good work! 
That fix (or, more likely, other changes implemented at the same time) has changed around some gear recommendations regarding custom stat distributions pretty drastically though.
I’ve generally prioritized Versatility over Mastery on my blood death knight and almost completely neglected haste and crit while using a “Max Defense” strategy, as that seems to work best combined with the disc priest in my mythic+ group.
With the old customization system I’ve simply prioritized Versatility and results were as expected. Using the new customization “wheel”, I’ve build my own stat priority of 2k Versatility, 1.4k Mastery, 400 Haste and 200 Crit. Results looked pretty much exactly identical to what I had before as I’m relatively close to those stats.
Since yesterday this isn’t the case any more and AMR wants to make some weird changes and deviates further from the aforementioned custom stat distribution:
| Crit | Haste | Mastery | Vers | |
|---|---|---|---|---|
| Targeted Stats: | 200 | 400 | 1400 | 2000 |
| Current Stats: | 456 | 414 | 1399 | 1935 |
| Recommendation: | 659 | 643 | 1353 | 1429 |
While I definitely see the value of some of the changes recommended (e.g. using 445 feet with Crit/Mastery instead of 430 with Versatility/Haste & socket) because of stats not included in the stat distribution (like Strength, Stamina and Armor), I’m not so sure about others (e.g. changing my crafted 440 legs with Mastery/Versatility & socket to 445 legs with Haste/Mastery).
Overall I’d be losing three sockets while also shuffling about 500 points from the most important stat (Versatility) over to the least important ones (Crit and Haste) - and gaining about 150 Strength, 560 Stamina and 170 Armor in the progress.
The main question isn’t why this is happening at all (could still be correct advice, even if it looks weird) but rather why this started with the fixes you implemented yesterday.
Maybe it has something to do with tweaking the extreme increases reported on another topic (Wrong DPS increase with customize stats in best in bags)? Or it could just be correct advice even if it looks weird and I just don’t like it?