I would like to focus on feedback for core rotational gameplay. I did not consider utility in this (not that it isn't important, it's extremely important) it's just something i want to discuss separately from core rotational gameplay in another thread.
I left out Vanilla and TBC not because i don't think people enjoyed them (i definitely like the idea of a "support" dps with the TBC mana battery style), but because i do not see a world where those playstyles have a realistic chance of returning.
The four styles i did choose seem to reasonably translate into today's game (albeit with certain tweaks), and are also very different from one another.
Cataclysm-I have seen a lot of people call this the golden age of shadow, and it seems to be the oldest playstyle that could possibly still translate.
MoP- A lot of people talk about wanting those shadow orbs back, and that is certainly a playstyle that would translate today. Having a completely different resource from Cataclysm and Legion makes this a unique playstyle to include.
Clarity of Power- While not as popular as other iterations, there are certainly people that really enjoyed it, and it definitely fits the criteria of being a very unique playstyle compared to the other options.
Voidform - This is of course a very unique playstyle from all the other choices, with a lot of players really embracing the playstyle, and a lot completely hating it. I chose Legion instead of BfA because most people seem to feel that Legion was the better iteration of this style.