I guess you could argue this is a skill factor thing and that people might enjoy being able to master this, but I truly despise it. I hate it so much. There's so much you need to take into consideration to play optimally - and put this into a raid setting where you have to handle mechanics as well. Pull it off and you're still just middle of the pack unless it's a fight with weird niche mechanics like Xavius, catering to S2M and making us look too strong.
To look at Xavius as an example, the top Xavius HC spriest parse is 635k dps. WOAH, WTF ! Shadow is so strong, better stack spriests! I guess that's what the wow community at large thinks. Now, let's take a closer look.
https://www.warcraftlogs.com/reports...pe=damage-done
He had double S2M during the fight, with the first S2M being a two target cleave with one target in execute. Full uptime on ToF, tons of insanity from SW: D. Tons of haste and MH stacks severely inflating his dps. Then we enter the last phase of the fight where he goes S2M again. He did 92.19m dmg to the tentacle adds you aren't even supposed to be attacking. NINETY TWO MILLION. He also had to manually target every add and apply VT and SW: P, while for example a fire mage has his Ignite spread automatically and hunters step back and enjoy free Barrage cleave.
Shadow supposedly is the king of single target execute dmg, but he wasn't much higher than the other dps on Xavius dmg. Casting dots on off targets doesn't really do much to your st dps and you still generate insanity by doing so and MF as a filler isn't exactly amazing, but still the st isn't amazing.