Eagles decks were just dealt a bitter blow.
How many eagles were you discarding a turn anyway? I don't think it will be that be an effect.
There's some spread between discarding multiple eagles per turn and having no effect. Horn of Gondor was cost-effective in an Eagles deck, because the Vassals go away when used (barring battle questing), the Winged Guardians go away if you don't pay, and Eagles of the Misty Mountains likes other Eagles to go away. Over the course of a game that's likely less than one resource per turn, though it's augmented by other allies leaving play. Not at all broken, but certainly useful, especially since Eagles are expensive. If you're running the full Eagles, Landroval, Thorondor's Descendant and Gwaihir have abilities involving something leaving play, and Meneldor's Flight specifically calls an Eagle out of play.
Now Eagles are too limited and expensive to use all this discarding to break the game by generating massive amount of resources. It was just a nice bonus that made an Eagles deck work better, either by providing a few extra resources for expensive Eagles or a non-tactics splash heroes. Totally non-broken, and fully expected when Eagles were introduced and the Horn of Gondor was one of a limited number of tactics cards in the pool. But now, Eagles only trigger Horn of Gondor when one is destroyed, and not a single Eagle is designed to be a chump blocker.
The funny thing is that Tactics really *shouldn't* be the chump blocker sphere in the first place. There's only two 1-cost allies, one is Outlands, so chumping goes against its trait strategy, and the other is a one-shot attacker. Leadership has three one-cost allies, one of which is specifically designed to chump block and another has only an enter-plays ability. An army of disposable allies is really Leadership's thing, not Tactics. Eagles were the one tactics synergy with Horn of Gondor, and now that's gone.