I tend to find that a lot of players have this strange notion that as long as a power is only usable once a day, it should be allowed to do anything and everything.
Take Platinum Scales, for instance. By the level a character can take platinum scales, the power grants a +8 or higher power bonus to all defenses for the entire duration of an encounter. Depending on your defenses relative to your opponent's attacks, this can be the equivalence of half damage to one fifth as much damage. Of course, it's only for one's person-so the enemy will just focus on someone else, right?
Well, not if you're a defender. And not if the entire party has similar mechanisms. The thing about daily powers is that, everyone has them. Everyone has three attacks, and as much as seven daily utilities by 26th level. That's a most severe case scenario obviously, but ultimately, even if in order for an encounter to be "fundamentally changed" every PC has to burn one daily power, that's still three encounters per day that are totally dominated by the presence of dailies, and many more if a party has access to a number of daily utility powers. Fortunately, there's a psychological impact in taking a daily utility compared to an encounter utility, which in my experience leads to daily utilities being less frequent, but the point stands.
Of course, as long as daily powers are not in and of themselves broken, there's no issue. The point is to demonstrate that, even as something only being usable once per day, that doesn't mean it won't fundamentally change the game-because there are a large number of them. In the same way I "only" use an at-will attack power twenty times per day.