A new test. I simply turned the predator health down to 10% in private match and timed
how long it takes fire to kill each predator. Assuming scout is still 1000 hp and berserker is 1500 hp I got the following results:
Scout - 1000 hp
Alpha - 1150 hp
Hunter - 1250 hp
Elder - 1250 hp
City hunter - 1250 hp
Valkyrie - 1300 hp
Samurai - 1350 hp
Berserker - 1500 hp
Viking - 1500 hp
This test will not account for damage resistance that Scout and Hunter are known to have, since update 1.06.