On the rare occasions I get matched with a party good enough not to need a healer, I admit it can be pretty boring.
But isn't that a problem in itself?

The balance between casual, midcore and harcore players has always been a tricky one to strike, and you're right to point that out. A lot of people tend to forget that after X number of years in the game, certain things can't continue to be ‘difficult’. But if a role has no use apart from making up for the shortcomings of others, then the design itself is poorly thought out. Just imagine a buff class whose role is limited to triggering one or two powers that can only be activated if the other dps forget their buffs. That would be a stupid design. And the healer... Well, it almost fits that design.