Perhaps because it needs Ice Beam to actually pose a threat to the set? Maybe because it is basically OHKOed by a +1 LO Outrage? (369 Attack +1 LO Outrage vs 448 HP / 240 Defense Vaporeon = 86.4% - 101.8%, a likely KO after Stealth Rock)
whether vaporeon does need Ice beam to possess a threat to mence is irrelevant.
Of course we are not talking about vaporeon sets which are not using moves that can defeat Mence ,as being used to defeat Mence.
I could have said ice beam vaporeon in particular but i think we all have the common sense to understand why that was not necessarry.
And i am not willing to further discuss the merits of that point. If you wish then you won't find me willing to comply.
Vaporeon that uses Toxic however may also be able to threaten mence (less efficiently than if it used ice beam instead) but that is beside the point.
This
it is basically OHKOed by a +1 LO Outrage
Contradicts with this
369 Attack +1 LO Outrage vs 448 HP / 240 Defense Vaporeon = 86.4% - 101.8%,
Anyways , vaporeon enters the field on LO mence with DD up and uses ice beam. Without SR up it's an unlikely OHKO for Salamence and with one i accept that vaporeon usually loses against Mence. I do agree that it is not the most reliable check against a DD mence which has already used DD.
I also agree that it is even more unreliable against a DD mence which has already used DD once and there is stealth rock in your area.
It can reliably check a Mence which does not have + 1 attack and with some luck it can also defeat a mence which has DD used.
By the way , bold max HP max defence vaporeon is guaranteed to survive a mence attacking with already boosted attack outrage.
Anyways , we should also mention the pokemon that can check DD mence which has not used a DD yet. It would be unfair to assume that everything that checks DDMence must be able to check a DDmence which has already used Dragon dance. The most reliable revenge killers , checks may indeed do that. But we will reach imprecise conclusions if we leave everything else out of the pciture.
Of course the list of things that can seriously threaten a DDmence which has yet to use DD is quite large.
Anyway , i propose a third subject more important than the category of "checks" .
"How a team can handle a Mence using a variety of pokemon , at different stages of the game" Before realizing what sets it has , and after doing so , or assuming what it carries.
Also it's important to note , the merits of gaining something from losing a Pokemon or two.
Getting into "real battle" simulation theoretics , would be a better alternative than "it 2HKOS everything therefore it's uber" Or "it's not uber because it simply can be easily handled" Or "assume that Mence has already DD up. Now assume what checks it".
Those arguments are leading us nowhere .
I say we imagine a usual OU team , and what happens when it encounters a Mence.