I think Salamence is a monster and extremely good in the current meta. A lot of the arguments in favor of banning mega mence stem from the fact that they're using it wrong, and are calling it bad because they can't use it. It's going to take quite some doing to get Mega Salamence to +1/+1 and behind a Substitute, and if you just disregard your winplan or the opponent's side of the field or whatever, you ain't finna win games. First of all, it takes two moveslots to get this degree of setup, and secondly, a lot of people here are falling back on 'redirection' as an argument. A lot of things are threatening given proper redirection. Heck, even NP (Footnote: Level 51, wtf is NP?) Mega Houndoom can be threatening, provided it gets a similar chance at setup. We should suspect redirection, and do a complex ban that prevents 2 pokemon from being allowed on the field at the same time when one of them learns rage powder, and another learns protect, and then spore and follow me are part of the complex ban, and so is kangaskhanite (sorry pwnemon I swear that was a mistype)
Mega Salamence's natural bulk work is pretty fkin naturally beastly and amazing. Its 95/130/90 defences are extremely helpful for setting up, and letting it set up is quite figuratively asking to lose. Substitute takes out an eZ amount of its health which it cannot recover unless it takes another moveslot or uses roost (other moveslots are [irrelevant] B. Bad[] or whatever moves you want to use to win every game easily because you're using mega mence. Sandstorm and Hail obstreperous this condition, and of course spread moves and attacks in general can provide some degree of annoyance if you don't get your redirector in / your Substitute up in time. Mence has too much control over its own speed, making stopping it more difficult than any other threat.
On the other hand, if you use Mega Salamence without Dragon Dance, you're forgoing a lot of the potential power Mega Salamence could have fucking garbage, and you're leaving it rather vulnerable to Landorus-T, Heatran, Aegislash, Rotom-W, and so on, which are all very common in this tier. Mega Salamence without Substitute is in a similar boat literally the worst set imaginable, and gets whittled down by Intimidate and spread moves in general since it no longer has a Substitute to block Intimidate and soak up hits.
What I'm trying to say is that Mega Salamence is broken, please ban.
Post Script MUST READ!!!!!!!!!!
Real talk tho, mega mence is op because you can just kill everything with an eZ dedge (nothing likes to catch a dedge straight to tha mouth), or you can subdd, or you can do pretty much whatever you want because jirachi redirects the attacks. Also, if you're in an unfavorable situation, then fucking switch out this is doubles, holy shit, why is switching such a foreign concept (switching only works in OU), and nobody who's anti ban knows how to use mence, or has ever looked at its stats or ability or anything. This is a completely objective statement, I have full smogon moderator support, and can we plz for the love of god ban the stupidest fkn mega to grace the doubles tier!!!!
edit: when I said stupidest mega to grace the doubles tier, I meant besides mega kang. Sorry about the confusion
SECOND EDIT: ok I legit don't know what I was thinking when I posted this, so let me make a real post. Mega Salamence is incredibly powerful. Its stats, ability, and typing all help it dominate most of the tier, and on top of that, it is also by far the most centralizing mon in the tier. If you don't have at least one dedicated mence counter, or 2-3 checks, you simply lose the game. I honestly don't think redirection is even what makes mence OP. The fact that a neutral Double-edge can bop most of the tier, while it barely sustains any damage itself, make it the sole destroyer or hyper/balanced offense (bear with me as I use buzz words to sound like I know what I'm talking about). I don't need to provide calcs or evidence, because other people already did that. Just trust me, it's broken! ban mega mence!!!