Let me tell you, that's not a good attitude to do conversation. I said it's OP because I PLAY HUNTER and I feel guilty each time I use it. Satisfied?
No, that still is an opinionated reason with no actual basis in gameplay balance, just, "feelings". Come up with a good reason before you start calling it OP, and then I'll be happy.
Fine, let's talk about other comparable cards.
Northshire+Holy Nova+Circle of Healing can give you >3 cards for 6 mana (and note: depending on board, you might not even need Circle of Healing)
Northshire is another of my favorite cards, and to be honest, I think it a bit OP as well... Well, let's say it's different because you have to prepare damaged minions to draw the cards. You need to deploy a minion first, keep it alive, make it damaged but still alive, before drawing a card. It's even more than the pure board control.
What you addressed, "Northshire+Holy Nova+Circle of Healing" actually gives you nothing.
That's why drawing >3 cards for priest is very rare because it's hard to manage.
Divine Favor can easily give you 3+ cards, for 3 mana, and 1 card, so, what is the concern again?
This card depends on your opponent's card advantage, it only makes the two of you back to tie. More importantly, it won't change the board control.
On the other hand, UtH draws cards as well as gaining back the board control. That's the big difference.
It's almost impossible to lose card advantage "on purpose", but it's fairly easy to lose board on purpose - you just do nothing.
We can also address the issue by talking about the counter methods. To counter a priest is easy, kill the minion or don't damage it at all. To counter a paladin, well, just play the cards.
But how to counter buzz+UtH?
I actually don't mind how many damages dealt by your hounds, I just want to prevent you from drawing too many cards. You mentioned playing Taunt instead of cheap minions. But taunt won't help in card drawing - not to say you even have the hunter's mark which works perfect with the hounds.
The only way is to play less than 3 minions all the time against hunter. I believe it is unfair to ask.
I play hunter and I win >7 out 10 games after the current patch. Whenever I drew buzz+UtH in the first 5 rounds, I never lost. I even feel a bit tired to play hunter because the routine is boring: let the opponent have board in early game -> draw a bunch of cards at turn 4-5 -> gain back board control, mark the heavy taunt if necessary -> now you have the board and significant card advantage, you win easily in the next 3-5 turns.
Though I don't have evidence of my statistics and I'm not recognized player either, I believe my statement is more than just the personal bias.
I hope this makes you happier than before.