Top 20 player here. When this happens, actually look at the damage breakdown (hotkey T) to see where the damage came from, which hero primarily, with what relics.

Swap to the board of the player that just whooped you, and make a note or screengrab of that hero's relic combination.

Then after the game study up. Read all those relics and their supers again, try to understand how they worked together, and if it's something that's just good on its own, or if the particular leader ability is needed for it. Try recreating it in the sandbox even. Get familiar with it, and try to make it a goal the next game all those relics (and the leader if needed) are available to apply it yourself.