Toss in a fighter to keep people where you want them and you've got a LOT of damage.
Mark
That last part there is key. Sure, in the above example of the 2 Hobgoblins and the Orc, you couldn't get all three in the burst. However, the players can try and work together to set things up. See below:
(1,2,3 are enemies, F is Fighter, W is Wizard, x is unoccupied)
x12x3x
xxxxFx
xxWxxx
Say the Wizard wants to drop Scorching Burst, but he can't hit all three guys. There's a simple solution here... Have the Wizard hold an action to cast Scorching Burst until after the Fighter attacks #3. On the Fighter's turn, he can shift up and to the right and then attack #3 with Tide of Iron. Whether he hits or misses doesn't matter, Scorching Burst will go off since the trigger was "when he attacks #3". If it hits, it will push #3 to the left so that he's adjacent to #2 and all three enemies will be caught in the burst.
Using teamwork like this, you can manipulate the enemies into closer formations to allow your Wizard to fire off his AoE's. Just sending him in alone and expecting him to figure it all out isn't going to work. The party needs to work as a unit, with the Defenders protecting the squishing and setting up CA and moving enemies to more advantageous spots if they have the abilities, the Strikers focusing their damage to bring targets down faster, the Leaders keep everyone alive and give them buffs to help them fight better and then the Controller does his best to find the best situations to use his powers in.
One of the other things that I think people miss about the Controllers is that you have
options. Going back to the example above, let's say the Fighter couldn't get around to the #3 monster. Rather than just casting Scorching Burst or Magic Missile, the Wizard should look at his options. Perhaps he could hit #3 with Grasping Shadows to help out the Fighter, or maybe hit #1 or #2 with Ray of Frost to slow them down and keep them off the party's back? This Wizard should always keep a good mix of multi-target powers and single-target powers (or at least, non-AoE powers, like Acid Arrow, that work on smaller groups). Yeah, the big AoE's are flashier, but sometimes it's better to just make one or two guys' lives a living hell, than to waste an AoE on just two enemies.