Hello. I recently created an arena deck with two improve Morale cards in it. When in a game, I cast the Improve Morale on a target with more than one health, and no lackey was added to my hand. My opponent also had a lackey card, and that did not trigger either. Thank you for your time.
This has been reported many times:
The Arena was even disabled yesterday to enable them to fix it. I assume it is back now, but I have not tried playing Arena yet.