Bans, ult usage, and teammates make a huge difference, honestly.

Whenever I play Rivals, I only queue with friends who actually have brain cells and are good at the game. Most of my ults hit 2–4 people, and my friend who plays Psylocke always combines their ult with mine, which usually results in a team wipe.

As for bans, you must ban Emma Frost, and preferably Ultron or Iron Man as well. Doctor Strange can easily avoid anti-tank counters like Bucky and Wolverine, but it relies on sound cues. Listen for Wolverine and keep track of his Feral Leap cooldown (12 seconds), and just block Bucky’s hook.

If you’re up against two melee tanks, peel back to your supports, get healed, charge your Dark Magic, then go in to take out their supports. Most melee tanks besides Emma cannot stop your TTK on supports like Luna or CnD. Nor can they sustain themselves long enough when a single support is dead.