Healing and Buffing alone isn't fun, but hitting enemies and buffing/healing together is fun.
The roles work quite well. There is no automatic need to define classes by roles, but it's most helpful to have all 4 roles covered. Linking Class and Role ensures that everyone knows which roles are covered and by whom. The classic Cleric/Rogue/Wizard/Fighter party that was the default assumption for 3E CRs was, in a way, also defining the roles groups had to cover. They weren't exactly the same roles as in 4E. The role of the Rogue also included "dealing with traps", which is not related to any 4e (combat) role. The Clerics "anti-undead" abilities were factored into the design assumptions on Undeads, and if you didn't have a Cleric, you noticed that when not fighting undead. That was of course a very small part of his role, but still an aspect no other "Cleric-like" class covered - Druid or Bards just couldn't do much to help there.
Precisely, those abilities were appropriate for the classes’ flavour, not dictated by artificial combat roles.
Now I think that making every class as useful in and out of combat is a good thing.
The "Healer" is a role required in every game, even outside of D&D. The moment people enter combat, they need healing. Not all games support much in-combat healing, but after combat, they still require it very often.
D&D requires in-combat healing to survive - Your "Meat Shield" won't survive for long when in melee with a powerful monster.
A game doesn't necessarily require buffs, but there is a tendency in most games to have them, because buffs provide a way of resource management & strategy - who do I grant the benefits, or against which opponent do I grant them?
It is "forcing strategy" in a way, but it is the kind of force that makes the game more interesting with it then without.
I didn’t say that healing/ buffing wasn’t necessary, just that it shouldn’t be a class’s main role, especially in combat. In older editions, nobody in my group would care if we had a designated healer or buffer in combat. All we needed was the healing potential, it could be one or several minor healers or just potions. Now that "inspiration" can restore hit points, it’s even easier to extend this ability to other classes. Same thing for buffs. Regardless of the old balance issues, do you think wizard shouldn’t have Enlarge or Haste because buffs aren’t the classe’s prerogative?
Meatshield on the other hand is necessary, because spellcasters would be really overpowered if they had enough hps to resist most attacks. But unlike the healbot or buffbot, being the defender doesn’t prevent you from having fun, whether others play along or not. You’re just useful by being there, in the way.
If it is of any consolation for you, the Warlord is an outstanding warrior, too. I think I hit more often the Paladin and might even have been able to out-damage him in a few situations. Though it was even more effective to give the Paladin a little help.
In 4e, an outstanding warrior is mostly represented by his warrior powers, not by his chances to hit. A Paladin is not just a warrior, flavour-wise, so he shouldn’t be as good at warriory things like raw damage.
The problem with the warlord is that it’s basically the same archetype as fighter. Just a fighter with inspirational and tactical talents. At best it should be a fighter build, not something to base a whole class on. Give him too much healing/buffing on top of fighting efficiency and he is overpowered (like the 3e cleric was), give him these powers at the cost of fighting efficiency, then he’s just a subpar fighter as soon as others don't cooperate.
I think to play a warlord though, you really have to focus on being a leader and roleplaying that (none of this Robin to someone else's Batman rubbish). You direct combat, push the other PCs (that is get them to use action points, giving them a good bonus to hit and damage) and generally be a leader. You make sure your group plays as a team and you get rewarded from the group success (that you directly co-ordinated) rather than the personal. If you are just there to have your PC dish out as much damage as possible, other roles would seem more suitable. YMMV.
For that you need others to play along. More often than not, a character who shouts orders or worse, a player always telling others what to do (I’m not sure which one you meant) is not cool and bound to attract "friendly fireballs" at some point.