The cleric, ranger and barbarian have the same role as the fighter in the battle?
The cleric's role might be to support the whole group, and he does this with buffing the group, healing the group, etc.
The Cleric when specced into a "melee hitter" setup, yes.
The Barbarian because he's in your face with a big honkin weapon.
The Paladin because he's basically a divine fighter.
I would really hate to see the cleric's only role as "support", I hate the "support" roles in any game, it's such a waste.
The ranger might single out an enemy on the battlefield and hunts him down, either with melee or ranged attacks.
I generally regard the ranger as a ranged attacker, otherwise he's a heavy rogue or a light fighter.
As a light fighter, I would say the ranger should have AoO, as a ranged build, he should get something else, as a heavy rogue, he should get something else.
Does their role in combat really have to overlap with the fighter's role in the combat? If any of these classes should have something similiar as the fighter's opportunity attack class feature, it should be the paladin, but give him something specific like opportunity smite or something.
-YRUSirius
I would say so. Any mainly-martial class should get AoO, perhaps there is some variance in how their AoO's work, when they get them and so on, but I certainly think that anyone with a big weapon, a big shield or the skill to know when to strike should get an AoO.
That's why I would generally break the AoO line between "mainly caster" and "mainly melee". Melee dudes get AoO, caster dudes don't. There would be specific exclusions and inclusions, but on the whole that's how I'd draw the line at the base.
But hey that's just IMO. I think most melee classes overlap with the fighter a lot more than you are giving them credit for. Not all fighters are intent on battlefield control. I think this is best demonstrated between the Knight and the Slayer in essentials. Both get AoO's, but the Knight's "Defender aura" allows him to do them much more often, because he's using those attacks as a means of battlefield control, while the slayer is using their attacks as a means to beat you up for doing something stupid. In WoW terms, the Knight is using his AoO's as a taunt to keep aggro, he's not gonna kill you with AoO, just keep you from killing anyone else. The Slayer is just sneaking in some free lucky hits.