On your Lati@s point, I really think you are ignoring the Pokemon Salamence is paired up with. Scarf Latios? Sure, just let me trap your ass with Scizor (who is the most common Salamence partner according to moveset statistics). Hell, I was recently using CBTar with Lum Berry DDMence so Latios was never a problem. Latias? Well, Latias never runs Scarf anyway so Scarfmence or +1 DDMence will always beat it.
Also, I don't know if I'm the only person who realized this, but Hippowdon kind of loses to MixMence. It'll also have a hard time beating last-poke DDMence if it doesn't run Ice Fang. Well, newsflash, Whirlwind is more common than Ice Fang! You also ignore the fact that DDMence often runs Lum Berry, which kind of defeats your status argument. AND, not only was Lum Berry used more than Life Orb according to usage stats, it's also the first item slash on the Dragon Dance set on its analysis! Don't believe me? Go see for yourself.
Also, I'd just like to say that it's not particularly uncommon to see defensive Politoed without Ice Beam. As for your Scarf Terrakion point, well, Terrakion revenge kills Dragonite too, so what's your point? And don't even bring up any "Oh, Multiscale, Multiscale!" bullshit because Multiscale is nowhere near as good of an ability as people give it credit for, often only helping for one turn in the entire battle that more often than not doesn't change the outcome of the battle one bit. Dragonite is also beaten by Choice Scarf Kyurem-B; Salamence isn't. Adamant +1 DDNite (AKA the ONLY DDNite that exists, period) loses to Timid Scarf Politoed; Salamence doesn't.
You argued that Salamence is easy to revenge kill, but in my honest opinion, Dragonite is actually easier to revenge kill, especially since Multiscale is a factor that is so easy to remove. It's revenge killed by everything that revenge kills Salamence and more (Scarf Salamence itself, Scarf Kyurem-B, Scarf Terrakion, Scarf Latios, Scarf Keldeo, Scarf Haxorus, Mamoswine etc.) Of these 7, only 4 reliably revenge kill Salamence. All of them reliably revenge kill Dragonite. Also, don't get me started on how piss-weak +1 ExtremeSpeed is, and no decent player is going to let their revenge killer get weakened to the point that +1 ExtremeSpeed will KO it. That's moronic. As for sweeping, a lot of physical walls like Slowbro and Hippowdon will hesitate to switch in on Salamence due to the mere threat of MixMence, and if you're actually going to throw your Skarmory right on in against a Salamence, you're a fucking idiot and are going to get nuked by Fire Blast (Dragonite needs +1 or CB to 2HKO with Fire Punch, so Skarmory can switch in much more easily).
That being said, both Dragonite and Salamence can sweep easily given the right support, and both can sweep far more easily than, say, Lucario or Toxicroak, who are in B rank. Therefore, both should be A rank.