Haha I do understand where you're coming from, but it has nothing to do with being prepared for them or not. The point is, what's the problem with using non-legendary Pokemon? I can say I've used one or two OU legends in some battles now and again but they most certainly don't take main spots on any of my teams. It's really just the principle of the thing, which obviously doesn't hold much weight in an argument about them. The only reason I keep bringing it up is just that the tournament would turn into people just using teams with majority legends in addition to Chomp, Blissey, Skarmory, etc. Battles here would just end up the same everywhere and probably very boring.
If you can already use one of them, isn't that enough to feed the need for them? Allowing Articuno and Phione would of course be fine, there isn't much threat in them what with low HP for one and extreme stealth rock weakness.
The majority of the triple legendaries have much higher amounts of HP and defenses than the majority of standard OU sweepers. Just look at Zapdos (which isn't always a sweeper, but you get the idea). Don't pick out little pinpoints of the Pokemon I'm suggesting, like I said the point is, why would you want to?
Mix it up, do something interesting, be an individual. Don't be the standard copycat/cookie-cutter Pokemon trainer. Even if that does win matches, is that the only thing that satisfies you? Haha I know it's just a game, so a lot of people are probably not as into this as I am. It's just the principle of the thing :P