I've also noticed that 4th edition characters miss a lot, but in my group that's sheer bad luck with dice. Especially our paladin reliably rolls a 4 on his attacks. But the whole group is like that, they've missed the big baddie 10 times in a row, always missing his AC by a mere point. To add insult to injury, the NPC that was just there to make sure they don't get lost in that mine got the kill.
(And yes, the warlord blew his daily in a miss in that fight)
As the DM, I went with it because I don't want the PCs to feel cocky and invincible. They've done badly in that fight, but they survived and it will make the next victory feel more worthy.
So yes, it sucks to miss your daily, but you get a second chance the next day. And as Mengu pointed out, in 4th edition it is very important to use synergy between characters to escalate each others attacks. Buffing each other for the daily is a tactic that players have to learn.
That said, I would not allow reliable dailies for free for everyone. Another reason is that this nerfs the fighter (and we don't want to have these discussions again...)
What I would allow is a feat that makes one power reliable:
Reliable Power (Feat, Heroic Tier)
Pick one of your daily powers. This power gets the Reliable descriptor.
