Do not allow Ob Nixilis pure removal decks on PvP nodes with the "burst" objective.
Title. Better yet, just fix the matchmaking on PvP nodes in general. If the game decides to match you up against a deck that makes it impossible to complete the objectives, or just counters your color-restricted deck completely, the developers might as well just be sending you a personal, "Hey, guess what? You won't be getting top rank thanks to luck that is completely out of your control! **** you! "
Seriously. It's stupid.