I imagine the best approach to 2v1 is to attempt to remove the 2v1 situation in some form. I am not certain how this might be accomplished. At the very least, you would have to remove your cooldown time as much as possible. Anytime you engage with another character you have to commit to some option which means you can be attacked from the other play. Hence the disadvantage. Hitting the other play towards the other one might not be the best strategy because it enables either person to piggy back off the other. Say you fthrow shiek back at falco, but sheik DI's up and avoids Fox, he comes in with an Usmash/Grab. You are now engaging Fox and fox protects Sheik from being knocked away anymore. By splitting up either character neither can assist the other anymore. So, you can say get rid of sheik off the ledge while going after Fox next. By succesfully winning these 1v1 situations you are never in a 2v1 ever. But, by knocking a person towards the other you are making it easier to recover from those 1v1 where the 2v1 team clearly wants ot get back into 2v1.