My complaint isn't even about the combo UtH decks. It's more about the card itself rather than the whole deck. I run a Mage control deck, and even with the maximum amount of control, it's impossible to contain this card.
I'm dominating the game and then suddenly there are 3-4 random creatures + UtH, say...
Bloodfen Raptor 4 dmg 2 mana
Starving Buzzard 3 dmg 2 mana
Stranglehorn Tiger 6 dmg 5 mana
Not even a combo UtH deck, just a normal Hunter deck with 2x UtH in it.
That's 13 damage right there, nearly half of my hp. Add the amount of Steady Shots and Explosive Traps which happened until this point and that's well around 20+ damage. Provided that I get rid of all these creatures by next turn since I run a control deck, or even if I don't get rid of them, provided that I freeze them until I can get rid of them, I'm still on a 4-5 turn clock just with Steady Shot, not even counting the probability of him drawing another Unleash.
If another Unleash is drawn, basically the game is over in 2 turns no matter how much you control the entirety of the game.
Someone is gonna come and say "Play Aggro deck then", as if Explosive Trap/Multi Shot/Expl Shot/Snipe doesn't counter that.
Now let's look at the card by itself and ignore all the examples above.
1 Mana, Common, Capable of giving Charge & +1 Attack to 7 minions.
That'd be 3.5 minions + 3.5 Attack on an average case for 1 Mana.
Let's look at other cards which give damage and/or charge.
Warsong Commander - 3 Mana - Probably gonna get nuked first turn
Charge - 0 Mana - Gives Charge to one creature, no attack bonus. You're not going to get one shot by a single creature in the middle of the game in all honesty.
Bloodlust - 5 Mana - 3 Attack to every creature. 4 Mana difference for 2 Attack ONLY and no Charge.
Point being, Unleash the Hounds is overpowered because you have NO chance to react to it. I don't know what they were thinking when they made this card. I don't think the designers realize that this game doesn't work the same way as Magic the Gathering or anything does. You can literally see this card coming, you can know that the player has it in their hand, combo deck or not, and still lose to it.
My suggestions for fixing the card :
Add one mana cost for each creature buffed. (ex; 5 mana for 4 creatures)
Change the mana cost to 5 mana. (Bloodlust is 5 mana, and even at this point it'll still be a better card than BL, obviously Charge is more valued than 2 attack, especially as a Hunter, if you know anything about this game.)
Make it single target. (Most reasonable change, given that it's a common card, and given that other classes have "similar" cards which are only single target such as Blessing of Might or Inner Rage/Charge)
Inb4 "YOU PLAY MAGE, MAGE IS OP TOO WHY DO YOU QQ", Mage is only "OP" if you don't know what you're doing. If you go ahead and play 5 creatures at once against a control Mage deck with 2 Blizzards, 2 CoC, 2 FN, 2 FS, then it's your own fault. Yes, Mage could be superior compared to many other classes at the moment, but at least you can react to it by not playing 5 minions at once or something.
Inb4 "PLAY TAUNT YOU MORON" Play the worst mechanic in the game to supposedly counter one of the 9 classes in the game, which won't even happen because it's simply going to get removed by Deadly Shot or Explosive Shot.