First, the Kazon Predator from the Delta sourcebook (p. 87) doesn’t have a value listed for Persistent!
Now for the meat of my question. Plasma torpedoes have the Persistent X damage effect. This means that after a torpedo hits, at the end of each Round the target takes an additional X points of damage for [Effect] number of Rounds.
Tholian plasma torpedoes have the Persistent 2 damage effect (whether the scale 2 Spinner or the scale 5 Weaver, both from the Alpha Quadrant sourcebook). This means that the Tholian Weaver, a ship as large as the Enterprise-C, has plasma torpedoes whose Persistent effect is shrugged off by a runabout with resistance 2. Should the value be increased for the Weaver or should Persistent ignore resistance? (The latter is dangerous, as the Refit D’Deridex in Gamma has a Persistent 8 plasma torpedo.)
I checked errata and didn’t see anything for either the Tholian or Kazon ships.