There is absolutely no point to walls or tanks in a 2v2 match. It's really just a matter of speed, power, and whether your partner is immune to the attack that you do. I mean, yeah I can run my Vaporeon with Wish + Protect, but that does no good when you have two sweepers wailing on it. It does you no good to run Blissey if they run a special and physical sweeper. What one sweeper lacks, the other compensates. I did decently well with a Crocune and Vaporeon only because it has Water Absorb to regenerate HP with Surf, but I was extremely vulnerable to Grass and Electric types. I've also tried the old Kingdra + Toxicroak Rain Dance, Surf set, and that does decently well until someone takes out the Kingdra. Really the only viable sets that this strategy has are the two that I mentioned. You can't do this with a Volt Absorb set, since no electric attacks work like Surf does. You could do a Flashfire set, but that's risky business because of the overused set that I'm about to mention. Everyone uses the Levitate + Earthquake combination, but then most people will run Levitators or Flyers as well, rendering that strategy useless. Weather support is common, but so is the Dry Skin set, so 2/3 of the time, Rain Dance hurts you, more than helps you. It's best to run two extremely fast, powerful sweepers, take out the supporting pokemon first, making the other one completely useless without it's partner, take a hit, they send out another pokemon that doesn't complement the remaining pokemon, and is forced to either switch that one or deal with running two offset. And then you proceed to revenge kill, revenge kill, revenge kill, until they're all dead. Choice items make revenge kills so much easier since two Choice banded or specced pokemon hitting the same target for super-effective or even neutral damage with STAB will kill it, tank or no tank. My favorite method of annoying people with 2v2 is using a scarfed Breloom whose Spore is 100% accurate. I spore the first pokemon that would probably kill me. Then I target the 2nd one, regardless if you attack or switch, you have two pokemon that are asleep, and if you switch more, it's possible to have all of them asleep. My other pokemon is dishing out damage, laying rocks while you figure out how to kill the Breloom.
on 2V2 battle, you need both pokemon to work together, like my Lapras and Vaporeon team, Vaporeon constantly heal Lapras with Surf while my Lapras take care of anything that imune to Surf.
Much like my Vaporeon + Suicune set, or Kingdra + Toxicroak. The problem is when someone takes out your key player, like the one that surfs to get the Water Absorb to work. And they can do that VERY easily by focusing two pokemon on that one, with the Choice items, you have no chance of survival. It's pointless to run sleep clause since if you do a 2v2 with a Darkrai and it hits (which it does) you now have 2 pokemon asleep at the same time, so that rule is broken. Also, if you manage to trap my Breloom or Darkrai, you've set yourself up for nothing but sleep inducers until they die.
2v2 requires a LOT more strategy and aggression, simply because you have two threats to deal with. I'm not a fan of it either, but I can sort of understand those that are: you can really see the immediate effects of any synergy. insanecrazy, check Smogon to see if there is a ruling on Dark Void in 2v2. I have the sneaking suspicion it's banned in Uber 2v2 because using it violates Sleep Clause. As for OU, Sleep Clause is still in effect, so no Spore abuse (however fun it may be). Also, your partner doesn't need to be immune to your attacks! You get a power drop if you use an attack that targets multiple enemies (and your ally, if applicable). It's best just to focus on your biggest threats one at a time, I've found. Counter their key player.
Lots of people play 2v2 Ubers. It's the fastest and most brutal metagame in existence, closely followed by Little Cup.
