Subtlety was an absolute masterpiece of spec design from WotLK through WoD. Since Legion it is ruined trash.
Shadow Dance used to be the most exciting cooldown in the entire game. It was incredibly versatile, offering a complete spectrum between extreme burst and extreme control depending on how you spent your energy and globals. Under the new design for Shadow Dance, the spec is plagued by:
Reduced options during Dance
Dance burst is nerfed because it happens more often
Reduced options when Dance is down
Regarding point #1, we had Garrote, Premed, Cheap Shot, Sap, and Ambush. Now it only allows us to use Cheap Shot, Sap, and Shadowstrike.
Regarding point #2, the depth of this point is underappreciated by many Rogues but it’s crucial to understand this to understand just how badly the spec has been ruined. Find Weakness used to ignore 100% armor (PvE) or 70% armor (PvP), but now ignores only 40%. This nerf was necessary due to the increased availability of Dance. This not only means that Dance is less impactful (in addition to being less versatile and interesting due to point #1 above) but also means that non-Dance openers are devalued as well. Find Weakness used to incentivize hit and run gameplay, getting restealths to pool energy and get huge burst in opening from Stealth. Now with nerfed Find Weakness and cooldown reduction on Dance from 223ing at something, we are incentivized to prioritize sticking to target to reset Dance charges as quickly as possible. This has ruined the once completely unique playstyle of Subtlety.
Finally point #3, arguably the worst of them all. Subtlety used to be a Rogue first, Subtlety second. Dance was a minute CD with no CDR and no charges, but when Dance was down you still had depth in the rotation and in the utility, with abilities like Gouge, Shiv, Poisons, Bleeds (not only the control of a physical DoT, but also setting up Sanguinary Veins), Slice and Dice (you would apply this in the passive phase while setting up for your next burst phase whether via Dance or a restealth), etc…
Now there is NONE of that depth outside of Shadow Dance. The spec is entirely designed around Shadow Dance, once the most exciting button in the game but now a stupid and mundane rotational piece which allows us the extremely one dimensional gameplay of spamming Cheap Shot.
Subtlety used to be the single coolest, most unique, deep, challenging, exciting, and fun spec in the entire game. The Legion and BFA editions of the spec are cruel insults to that awesome history.