Well, giving up class balance is a strong way to put it. I would rather say de-emphasizing precise balance.
Sorry, should have said giving up /some/ class balance.
And yes, I'll accept less-balanced classes, not simply for the sake of being less-balanced, but accepting that lower values of balance may be a necessary prerequisite to see experimental design that excites me to try that game mechanic.
'Experimental design' is an interesting way of putting it. I've been wondering if maybe 4e really needs to formally split into a simplified 'Essentials' and an 'Advanced' version. Maybe it really needs to settle into an 'Essentials' on-ramp, a 'Standard' balanced version, and an 'Extended' version with many more novel or experimental mechanics, the most workable of which eventually get added to the 'Standard.' A little much, maybe, but it might go a way towards satisfying a broader fan base.
After all, sometimes it's your flaws that make you beautiful.
That's a truth that many seem uncomfortable admitting. It's clear, for instance, that a lot of 4e hate was from 3e fans who loved 3e for the very flaws 4e fixed. The 'sacred cows.'
Doesn't mean the sacred cows weren't flaws or that they hadn't been holding the game back for decades, but it's worth recognizing.
It's true - though, myself, I've always found healing surges to be more of the dividing line than daily powers. A group might press on without dailies, but will be very cautious about doing so when out of surges. And that hasn't really changed.
(Except, of course, we've got the upcoming Vampire class which does mess with that! Though it sounds like it has a decent mechanic for keeping its healing limitations on par with the rest of the party.)
Joy.. Surges are certainly a good indicator for when it's time to rest. (They could also be said to be a 'daily' resource - so if classes with dailies consistently had fewer surges than those without, maybe there could be some 'balancing' there, too? Meh, probably not.) But a DM whose story calls for a very long adventuring 'day' would have to scale back encounters, which would mean the surges would be burned through more slowly. And, if daily resources become a source of class imbalance, some players may well be tempted to emphasise the situations that make thier class overpowerform - by insisting on resting frequently if they have dailies, for instance (certainly a very common thing in 3e).
Yeah, my point wasn't that it was the same disparity of balance, but that numerous types of imbalance can already exist in the system. The split-stat classes. Weapon damage vs caster damage, especially for strikers early in the edition. Or the difference between direct striker mechanics like Quarry and Curse vs the harder to quantify benefits of the Barbarian. Unless we keep each class absolutely identical to the last, fluctuations in ability will exist.
Nod. Since some sources of imbalance are unavoidable - or 'worth it' in some way - it only makes that much more sense to avoid it when possible. Aside from the desire to have casters be superior (OK, 'feel different') from non-casters, I don't think any of essentials other goals (simpler to build/play classes, being the big one) would have been any harder to accomplish while retaining AEDU as an underlying commonality for all classes, even if some builds put it 'behind the curtain' in some way.
Now, all that said? Your point - that just because perfection can't be reached, is no reason not to try - is a good one. Other imbalances shouldn't excuse letting worse ones crop up in Essentials.
But my thought is that any issues from Essentials ones is not actually worse than similar issues that have cropped up before.
Even if they're not worse, if they're /in addition/, they're still making the game worse. If Essentials had degreaded class balance a little, but fixed the 4e issues with encounter balance, for instance, that might be judged desireable or a wash. The things that Essentials improved, however - like the different format or the more mechanical differentiation of classes - have been highly subjective, and could have been done without messing with class balance.
A good hypothetical example would be eliminating dailies: Eliminating dailies /entirely/ from the game would improve encounter balance. Assuming the class's various remaining powers were still balanced (or adjusted to be balanced), that would be an improvement in balance. But, it would come at the cost of the much more subjective feel of 'narrative control' or 'drama' that dailies bring to the table.
Pretty much every new release, we've heard that one new class is going to be so much better than all the rest, or so much worse. And rarely is that the case - they aren't all equal, but they are all on par and capable of playing the same game, in the way that the imbalances of the past couldn't always achieve.
Often, a new class is noticeably sub-par, like the Seeker. If a new class isn't made pretty butch out the gate, the lack of potential synergies in its smaller power list will make it less effective than older classes with more support.
One direction Essentials seems to be moving in that might not be all bad, is towards more builds of existing classes, rather than more new (and harder to balance) classes. Which is a good idea, as long as the new builds can leverage enough of the existing content for their class.
Honestly, it is possible you are correct - an Essentials character vs a non-Essentials character might work fine side by side for one encounter, but reveal underlying flaws over the course of a campaign. I don't think it is likely to happen... but I also don't think we will know for sure until much more time has gone by with such classes in action alongside each other.
We'll know for sure, years down the line. When people are forming a consensus that this or that class 'was always a bad design....'
For myself, I do like to see WotC experiment, even as I can understand concern over what those experiments will do to the game. And, honestly, my main concerns with Essentials is more over the ever-greater focus on Expertise and other super-powered feats, and what that does to the game - so it isn't as though I think the WotC design team can do no wrong.
Ah, 'experiment' again. It's a nice idea, but we need a secure location for these experiments, so no innocents are caught in the blast radius.

I certainly agree about the odd solution to the complaint that Expertise feats were too 'must have' and therfore flavorless non-option 'taxes.' Make them /even better/. (!?!?!)
But in this case, I haven't seen any signs that they failed in their goal - to create new builds whose resource allowance is different than the rest, while remaining fundamentally balanced with the earlier options. But I could be wrong - time will tell, far more than any math or theory we can lay out on the table right now.
I remain unconvinced that 'reamaining fundamentally balanced' /is/ part of the goal. I think that balance was knowingly sacrificed. Either as a trade-off to meet other design goals, or for it's own sake, to woo the fled-to-pathfinder set (or both).