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Imaro - I think you are taking a fairly simplistic view of encounter design. In all honestly, it sounds an awful lot like a 3e design - each encounter is self contained, does not overlap with other encounters and all of the actors in that encounter are known at the beginning.
This is certainly true in the vast majority of modules designed for 3e that I've seen.
4e seems to be moving away from that, from what we've seen. Your encounter should span a number of areas, with various actors entering the combat at various times. In the GRZ podcast, they mention the Lurker role for monsters - something that hasn't been exploited as much in 3e. So, you open the door to the room, see the four undead and think, "Hey, 3 standards and an elite" and open up with your dailies.
Only, you can't tell which one is elite, so, which one do you blast with a daily? And, then it's the monster's turn and suddenly, even though you've blasted two of the baddies with your dailies, a fifth monster pops out of the woodwork (like the wraith can do) and now your dailies are expended.
Plus, you might just have blown dailies on minions. Maybe those four baddies are just minions - zombie minions for example, and you've just dusted them all, only to find that those four brutes come crashing out of their coffins.
Opening with dailies in the first round requires you to have a fair bit of knowledge about the fight in front of you. It might very well be that you will do so sometimes. Particularly if you are ambushing someone for example. But, I highly, highly doubt that it will be the best option in every fight.
In 3e, where encounters were typically self contained, with the actors known beforehand, combined with the fact that any of those actors can kill you in one round, it made perfect sense to blow through your big weapons ASAP. The fight was likely only going to last three, four rounds anyway, so, use it or lose it.
We know that fights are meant to last much longer now. Your example gives the monsters WAY too much firepower. At no point should the PC's be facing creatures of equal power. You have the baddies killing the PC's in the same amount of hits that the PC's require to kill the baddies. I think you will find that encounters should never be that powerful.
Again, I think it's a 3e prejudice, where it was likely true that a given monster could kill a given PC with equal numbers of rounds of attacks. In other words (cos that's an ugly sentence) a CR 10 monster that takes 8 hits to kill, could probably kill a Lvl 10 PC in 8 attacks. We know that this isn't true in 4e. A monster that takes 8 hits to kill probably requires significantly more attacks to kill a PC. Why? Because the monsters aren't meant to be fought alone, like 3e monsters were.
So, your dogpiling monsters will likely take two or three rounds to kill a PC with standard attacks, while the PC's can likely do it in half the time.
I think that's where your example goes wrong.