My general (unfounded) suspicion is that mob damage tables are mostly correct, but there is some sort of mitigation/damage reduction occurring that has yet to be explained. The only way the tiger could do regular damage to a higher armour Tips and 1-3 damage to joana is if there is some mitigation occurring for joana and not tips, or if they are on different shards/layers and for some reason the stats are different between the layers (extremely unlikely/impossible), or the tiger in the joana clip just happens to be born with a disability. But I should probably leave the baseless conjecture to the experts.