I know, blasphemy. Hear me out, though.
Crits are great against Minions, PCs, and Nemeses. Against most rivals, though, my groups have always been sorely disappointed. A lot of the Critical Injury results are interesting if you're settling in for an extended battle against a hated foe, but for the most part, the job of Rivals, like minions, is to provide a challenge and then die. Most of them aren't going to come back in a few sessions with a cool scar from the crit you once gave them (some of them should, when it makes sense, but that's when a Rival becomes a Nemesis). I've had a number of fights with Rivals slog on because they were tough as nails and mildly hampered by crits.
I'm considering giving my players the option, before rolling the crit, to treat it as extra damage. Roll d100 as usual, and the target takes extra damage equal to the Severity. Assuming no modifiers, that's a 40% chance of 1 extra wound, 50% chance of two, and a 10% chance of 3. It's not much, but it's fast, it's less for the GM to keep track of, and it ends the fight more quickly.