how

(Yes, I get it's a joke. Corpseing intentionally.)

Mainly depends on the DPS chosen. As a general rule, you can safely assume the following as a baseline to improve your odds:

If there's 3 melee DPS (mDPS), 2 mDPS and one ranged DPS (rDPS), or one mDPS and 2 rDPS: then just get a Groot, Magneto, or Strange for your Vanguard (VG) and then choose 2 from Luna, Cloak & Dagger, or Jeff. Alternatively, forgo a VG altogether and go two of those Strategists and any one other Strategist.
If it's 3 rDPS, then your two options are to go with two of the aforementioned VGs as well as either Luna or Jeff.

Obviously it won't guarantee the victory, but it will greatly raise your odds. I've won a fair few games where 3 DPS auto-locked because I encouraged the other players to meet the needs of the comp. And, y'know, that's ignoring games where those DPS were willing to pivot when politely asked for one to switch to VG or Strategist. Most people want to win and are willing to cooperate with others.

my team won with only dps lol

Damn this is some voodoo shit :o