"life stealer" also appears on ashbone pyro and is at 30%. the text is identical other than being 30%. The only difference is that a little picture doesnt show up with a bicep that says "life stealer: x% of the damage dealt by this unit will be added to its health" however the ashbone pyro lifesteal functions identically. I dont see any issue with the literal leader of the bandits and also the only real T4 bandit card had a better lifesteal.
EDIT: and the lifesteal of ashbone pyro can be upgraded to 50%, however it still has the same text on the card simply saying "life stealer".