I guess the real question is are implement users really dragging a whole lot on potential damage output?
Well, if a player were to make the jump from playing weapon-users to an implement-user, here are the adjustments he'd need to make...
* Get used to doing d6's and d8's as your base damage.
* Get familiar what the word "resist" means.
* Get used to the idea that when you take a feat that grants a damage bonus, it won't apply to every single one of your attacks.
* Don't fuss over getting an item for every body slot anymore, as they won't dramatically improve your character's attack output.
* If you want a basic attack, you have to expend one of your two at-will power selections to get it, and even so it will be weak.
There's also more nitpicky stuff, like not having the ability to customize his attack so that it gets high crit or brutal or an extra +1 to hit, but if I kept going on I'd just wind up diluting the major flaws, which are those above. Basically, his base damage will start lower than a weapon-user's, and he'll fall farther behind as feats and items broaden the gap.
Realize, these are universal adjustments he'd need to make, not class-specifc ones. Some clever ducky no doubt is going to be tempted to play
-for-tat about how an implement-user transitioning to weapon-user would have to get used to not being able to blast five opponents at once, but the truth is most implement users can't actually do that either, as bursts and blasts are predominantly 3x3.
Are weapon users really able to achieve the kind of overall battlefield control and wide ranging control effects that casters can? It seems to me that a caster can achieve stuff that a melee character really can't. It seems to me that a caster can achieve stuff that a melee character really can't. There's a lot of utility in being able to mark out a chunk of the battlefield anywhere in a wide area and create a zone or wall there.
Here's the thing to bear in mind: all classes can do stuff.
If a character doesn't have a daily power that creates a zone or wall of flame, then he has some other daily power in that slot instead that does something spiffy in its own right. And that's true whether or not that character uses implements, weapons, or both.
Let me make it even more straightforward. If my implement-wielding character fires off a bolt of flame as an encounter power, on what basis should I be doing only 2d6 or 2d8 while some other guy with a bow is doing 2d12 with his encounter attack, and yet another dude with a mordenkrad is doing 6d6 with brutal 1? Because somehere on my class's list of powers I have an option to make a zone or a wall (that I didn't exercise because I picked the flame bolt instead)? What does that have to do with it?
* We're all making a single-target attack, so that's a push.
* The flame bolt probably has some kicker effect like splash damage or dazing, but the other guys' weapon attacks have kickers too, so that's also a push.
* I'm targeting reflex while they're targeting AC, but then again I'm not getting a +2 proficiency bonus either. Some monsters might have really low reflex, but others have really high reflex, but most of the time it's 2 less than their AC (imagine that), so let's write this off as another push.
* Our ranges are all over the place: ranged 10 for me, ranged 20/40 for the bowman, and melee for hammerdude. Maybe hammerdude should have an edge, but by that logic shouldn't I have an edge on the bowman?
OTOH, if I lob an area burst 10 that stuns every creature it hits, then yeah, I can see where I oughta be taking the shaft on damage. But that's because of what the attack itself is doing, not because I'm using an implement to deliver it.
This is a blockbuster of a game balance issue, and if folks had to choose one thing to get upset over with 4e, this should be it.
Instead, nobody really gives a damn. Go figure.