Q: Can I use Get Over Here! to re-engage with a minion that I am already engaged with?
A: You cannot engage an enemy that is already engaged with you. -(Developer Ruling, Hall of Heroes)
Attack.
Hero Action (attack): Deal 1 damage to a minion. If you have the Aerial trait, engage that enemy.
Q: Can I use Get Over Here! to re-engage with a minion that I am already engaged with?
A: You cannot engage an enemy that is already engaged with you. -(Developer Ruling, Hall of Heroes)
I feel like this is one of the worst cards in the game, even for Thor, with the ruling that you can't re-engage an enemy that is already engaged with you. That ruling makes the card basically useless in single player and it's so situational in a multiplayer game that often times you're just trading a card for 1 damage on a minion if you're not pitching it for resources. Everything about the card is too situational. There has to be a minion in play, you have to have aerial, and you need the minion to be engaged with someone else for the card to have any sort of value as the 1 damage on the card is negligible unless you need to pop a tough status card; and, Aggression already has Piercing Strike which fills that role better.
Virtually useless in solo (shame: if there wasn't a rule that prevents you from re-engaging a minion you've already engaged, it could have been an interesting strategy for Thor and/or decks running the recent Aggressive Stance), but I would almost always include it in an Aggression Thor deck when multiplayer (I guess it's no coincidence that Thor is in the picture...).
I hope they'll eventually change that re-engagement ruling. This card is the exact reason why it doesn't seem unbalanced to me to allow heroes to re-engage a minion they've already engaged, as it only fits niche - and frankly far from op - strategies (see above; I can also think of Lie in Wait and Patriot).