It's also higher ladder. If we don't judge teams on score or ladder ranking what do we judge them by? I'm pretty sure my GXE on that account was also 80 or higher at its peak (which I've been told boils down to on average I have a 4/5 chance of beating any player I play), currently it's 79 - go /ladder Kerghan, I'm not screen-shooting it for your amusement.
Bottom line, it's perfectly viable. It has the same bulk as Porygon2 and more bulk than Cresselia while being a lot more of a nuisance (personally I find Porygon2 and Cresselia lack a bit of power to go with it's high defenses for my liking so I like pure set up, but as Darkreaper215 seems more on the bulky offense side of Trick Room than the hyper offense which I favoured arguably at least Porygon2 suits his team better - however as Dusclops would provide a fantastic transition into Mega Heracross as well as spreading burns with ease it's probably worth testing in the Cresselia spot).
In terms of the Knock Off weakness (which is equally applicable to Porygon2 which loads of Trick Room teams use and has the same bulk), it can take all relevant OU unboosted Knock Offs to set Trick Room and then underspeed and burn/memento on the second turn to provide a seemless transition to something willing to take advantage of the Trick Room turns. Its bulk, without recovery, is more than enough to allow you to set Trick Room multiple times (especially towards the end of the match, when you can go for a sack to bring something strong in to leave Dusclops to set TR again right at the end of the match) - and further you can just run Pain Split in place of Toxic, which with Dusclops' horrible HP stat (it's defensive bulk comes from it's sky high defense scores, not from high HP like you have with something like Wobbuffet) would be great recovery. Point is, I never saw the need to run recovery because it's defenses are good enough in the first place for multiple TR setting.
Viridi, who made the disparaging comment to begin with, afterwards PMed me to say he looked at my team and said it was a viable set - just that it might not fit on Darkreaper215's team, which could be the case but I still think he should give it a shot. It offers different advantages to Cresselia, which through play-testing have potential to suit his team better (as I mentioned, being a bonafide lead into the power house that is Mega Heracross - which Lunar Dance switching does not provide to the same extent at all).
You fundamentally do not know what you are talking about, and seem blinded by the arbitrary tier rankings Smogon ascribes to pokemon rather than using your own judgement to tell you what is viable for a certain team archetype.