Oh, you wanna play that game then?DW OU was the third-most played ladder on Smogon PO at its peak. It had a pretty big playerbase. It had analyses going on the site.
The purpose of bringing up Chandelure is to give context. The whole 'oh shit' factor Chandelure had on players fearing its OU release as well as some (a limited amount of) people who had played DW does not compare to Mega Gengar, which has nowhere close to the potency and dominance of Chandelure as a Pokemon.
These comparisons simply outline the limitations of Mega Gengar.
Mega Gengar doesn't need a Choice Scarf to function. ST Chandelure did, as otherwise it was simply too slow and not bulky enough. I'd argue that Mega Gengar is more potent than ST Chandelure ever was, especially with things like Destiny Bond and (post-Bank) Perish Song in its movepool that let it do more than ST Lure ever could, and, once again, not needing a Choice Scarf to do its job. The fact that ST 'Lure was practically forced into running Scarf (I know other sets existed but they were nowhere near as effective) really limited its potential, while Mega Gengar doesn't need to worry about that.
Four moveslot syndrome doesn't make anything not good.Then what set are you using? Gengar cannot have Shadow Ball/Taunt/Pain Split/Disable/Substitute/Focus Blast/Perish Song/Destiny Bond all on the same set. It's versatile, I recognize it, but by forgoing any of these moves Gengar is left open to one or more kinds of check.