It depends on the tier you're playing at.
At epic, for instance, you can reasonably expect a Wizard to open most encounters with a daily, and see the combatscape change from 'difficult fight' to 'cakewalk.'
In the limited play testing I've done with higher level characters ... I find At-wills to be much predictable in terms of defining what you can expect from a class as those will always be available for them.
At low levels, at-wills matter the most purely due to lack of other options, but that actually quickly solves itself.
Later on, if combats average around 6 rounds, that's enough time for people to do about 4 encounter abilities... which leaves 2 rounds of daily/at-will to work through. I find it's fairly common for one person to use one daily each combat so you might see 7 round combats if people don't, and then the big fights will tend to burn a lot of dailies so that works out okay. But, in general I find that things like 'Blood Pulse' and 'Healing Strike' matter a lot more than the once a day Beacon of Hope or Wall of Fire.
Edit: As an aside, I think Fighters desperately need an at-will that allows them to make an attack against a single opponent that is slightly better than a basic attack. Since Reaping Strike isn't even a sure kill against minions I would like to see something that is useful even if you don't want to move the target. I dunno, add your CON modifier or something.