This. Both are quite true. Controllers were initially designed, I think, as the role that attacks multiple foes. The problem is, every class eventually gets access to these abilities. Status effects don't match up, either, especially with Rogues dazing and blinding everybody and Wardens slowing and knocking prone like nobody's business.Controllers get a bad rap because some other classes have a few controller type powers that step on Controllers toes.
But the Controller can step on toes too, such as a striker's, if he catches a bunch of mobs in an area spell, or one of his zones is used to repeatedly damage a creature via forced movement. It adds up.
People see this and think: "Oh, Controllers are unnecessary, because if we really need to slow/daze/immobilize an enemy, or attack multiple enemies, somebody else in the party is bound to have at least one power capable of that." The thing is, multi-target damage and status effects are only components of the Controller class. The most important aspect of the class is their ability to, well, control. To literally re-shape the battlefield, whether that's due to plunking a wall or dangerous zone down in the middle of it, creating a zone of concealment, or by pushing or sliding foes around like crazy.
Also, Controllers do scary damage in certain situations... just not all against one target (which, admittedly, is usually weaker, since strategically you want to focus fire and drop a foe as quick as possible). But I recently saw a level 9 Covenant of Wrath Invoker do something like 150 damage in a single turn... while also dazing, pushing and blinding everything in the blast. It was freaking scary.
It took WotC a bit to get the 'Controller' role right, I'll give you that. The Wizard was definitely ailing for a while. But it has hit its stride now, and it is really a thing of beauty. Not necessary for a successful party (no role technically is), but if you see a good one in action, you can appreciate it for what it really is.