let me put it to you this way.
In a multiplayer match with single elimation, as in the player doesn't come back to life if they die, if two people gang up on the same guy, they will kill him faster and then have only one opponent to worry about, which makes things easier. And that is if everyone is evenly matched and nobody has an advantage.
It is even more important to act this way if one side does have an advantage, or one saide has a particular disadvantage in regards to one of their opponents. Taking out the easiest target first is the smart thing to do. A team battler should be prepared for this either with aid ally cards, parries to deal with their weaknesses, or other things of that sort to keep that weak ally from being overrun or keep themselves from being overrun if they are the weak one.
Also, team play is different from one-on-one play, so sometimes it is best to construct your decks specifically for one format or the other, some cards are distinctly more useful in one format while some are good at all formats.