This card is sort of the classic Aggression card, but in a negative way, it kind of exemplifies how the designers don't like to give Aggression good cards. 5 damage for 4 effective resources is just not good enough, you should be getting 1.5 damage per resource. But the problems with this card go beyond mere efficiency. It is an expensive card with fairly high damage, which is not particularly good as it tends to overkill some of the minions, you would often rather have cheaper cards that do damage in smaller increments. More significant than that is that the cost of 3 is high enough to reach the point where playing a cost 3 ally would be a more efficient way of dealing damage. But the most disappointing thing about this card is that even if you do make a point of putting it in your deck and not putting in any better alternatives, and you get into a scenario where you really do need to deal damage, it can still end up sitting in your hand because most heroes have a fair number of hero-specific attack cards, and designers are not shy about making hero-specific cards which really are very efficient and far better than Uppercut, so you would rather be playing them.
Uppercut isn’t useless, sometimes you draw it when you need to deal damage and don't have a better card. And it kind of comes into its own at the very end of the game when all you care about is dealing damage and you are happy to find any card in your hand that focuses purely on dealing damage. It is just a disappointing card that I stopped using once I got enough expansions to have more choice in what cards to put in the deck.