Jirachi and Latias are absolutely not on the same boat of Salamence. The former does not have the same destructive power of Salamence. Sure, it has a move to screw up almost every one of his possible counters, however it has much more reliable checks. Swampert, for example, can withstand almost everything Jirachi dishes out bar Grass Knot, boosted Psychic and Trick. It is not a counter, but it has a good degree of reliability - much more than anything could boast against Salamence. The same can be said for Latias, when you have Blissey, Scizor and Tyranitar able to check almost all of her sets.
You people keep thinking as if we are blaming Salamence for the fact that it has a diverse movepool, where certainly we aren't - heck, even Dragonite has a richer movepool than big brother Mence. The great feat of Salamence is not diversity. It is, rather, the ability to screw the entire tier with just two movesets - DD Mence, and Mixmence. There is anything which can switch into both the movesets with even remotely the same reliability of the checks I mentioned for Jirachi, Latias, Gyarados, Infernape and so on. If you guess the wrong of the two movesets (essentially a coinflip), most times you put yourself at a huge disadvantage - you cannot even let the Pokémon in game to scout the set, because if it is a Dragon Dance variant and said Pokémon cannot block the setup you are fucked anyway (unless you have a Scizor, but we have said countless times how easy is to get rid of Scizor).
Again, don't try this. I know perfectly well that the notion of counter is a surpassed one. Besides, you really cannot say Blissey is a counter to Latias or Swampert is a counter to Jirachi. But there is a great difference between "X Pokémon has no counters" (which, as you said, is perfectly acceptable in this metagame) and "X Pokémon has no reliable checks and beating it most times is a coinflip" (which is beyond what any other Pokémon in OU can boast). I mean, sure, most times you limit yourself to check threats rather than counter them. However, when the only ways to check a threat offensively imply using a Magnezone bait (Scizor), a Pursuit bait (Scarf Gengar, Scarf Latias) or, even worse, hoping into a Speed tie (Scarf Jirachi, Scarf Flygon), whereas defensive and/or stallish teams have almost no hope, there is something wrong. Besides, all this need for scarfers just to check a threat reminds me a lot of how, in Ubers, you cannot leave home without a Scarfer. Sure, I know this last fact hasn't strictly anything to do with Salamence's tier status, but it is nonetheless interesting.
I won't commenting on this part, since what I said before shall suffice. Also, that's the reason why I do not accept "Cresselia" as an acceptable answer to Salamence.
Again, the threats you have pointed out are much more easy to check, or even counter, than Salamence. The wrong fact is that, whereas you have viable answers to these Pokémon, you have none for Salamence.
The point is, if I wanted to make a team impervious to Tyranitar, or Latias, or Gyarados, or Jolteon, or Suicune, or "what the hell", while still having a viable team in my hands (although with his weaknesses), I could. The same thing, with Salamence, is nigh impossible. Having multiple scarfers on the team makes you weak not just to a single Pokémon, but to an entire playing style (aka stall). Hoping on Scizor to reliably check Salamence is an illusion too. The fact that, despite the fact that you prepare for him, Salamence can still fuck you up, reminds me less of Infernape, Gengar and co. and more or Garchomp. I'm not saying Salamence = Garchomp, but rather than, like Garchomp, making a viable Salamence-proof team in this metagame is completely impossible, and at the moment, Salamence is the only Pokémon in the tier to boast such a feat. Hence why, at the moment, Salamence is probably the only Pokémon in the tier to warrant a test.
