The issue is really that the class name, and indeed the term for the role, 'leader', is not very appropriate.
Well, the 4e designers could have called them 'buffers', but then it sounds like you're talking about someone who works at a car wash, or perhaps on the set of a pornographic movie. Or 'combat supporters', which sounds like the proper term for a military-issue jockstrap.
But there's nothing wrong with the class itself.
The warlord in our group is great. He's like Dr. Phil in chain mail.
I have to admit, this particular strand of the discussion perplexes me. D&D has always been a class-based game. Which means there's always been a significant amount of friction between the mechanics and in-game logic. Why can't single classed (and honor-free) fighters learn to stab people in the back? Why is it only rogues can learn to watch their backs? Why are advantageous fits of
anger the sole province of barbarians? These are gamist design choices which, if you're in the mood to be apologetic, can be dressed up with logical-sounding explanations.
It's time for a (barely) appropriate analogy. Complaining about the gamist aspects of D&D 4e --for instance, the warlord-- is a little like a man who's been dating a transvestite for years. One day his transvestite partner buys a new dress, and suddenly the manly-dressing partner says "Wow. You're not really a woman. I'm no longer attracted to you. We should break up". All because of the new dress.
Now an outside observer might be tempted to say "You never noticed her large hands before? Her Adam's apple? Her
penis? I though you knew all along and were cool with it."
Now no one can explain the rules of attraction, and heart is a lonely, not to mention blind and insane, hunter. So there's nothing
wrong with the guy who dumps his transvestite girlfriend of several years because of her new dress, in the same way there's nothing wrong with gamer who objects to 4e-isms like the warlord, but accepts all the equally gamist design choices which have been part of D&D since the beginning.
But neither can they be explained logically. There are, after all, matters of taste.