I haven’t used the card yet but I did steal a few with my Gretta deck. I couldn’t keep them alive enough to really notice them be of any value.
It’s important to note that he duplicates the Hero’s ability, not add to it. If the ability is 25%, or 1/4 then normally it’s like rolling a 4 sided die. With 1 Lackey in play you now roll 2x 4 sided die, not 1x 2 sided die. So if the Hero’s % is really low, like 5%, then it doesn’t mean it’s going to trigger all the time, it just means you’ll get more rolls of the D20, and every 20 is a hit.