I had to do that this weekend. The group (five level 5 PCs) were facing off against ten level 3 NPC's with +50ss, AT 4, DB 5. They should have mopped the decks with them, but every player was rolling poorly and all the crit rolls they made were no higher than 27. It was just a horrible set of dice rolling for everyone. One NPC open-ended twice and rolled high on the Krush crit and shattered the elbow of the weapon arm for the only tank in the group.
Two players and an elemental squared off on the NPC captain and actually killed him from HP loss! (+25da, AT 1, DB 5) I didn't want a TPK, so I gave a morale check to the NPCs, one of the players rolled Intimidation and it was decent enough that the crews just stopped fighting once they saw their captain go down.