Even beyond the flavor issue the classes operate vastly differently.
Our wizard
Our fighter
The rogue
Our warlord
Our swordmage
My cleric
All classes play the same? Not even close.
I just wanted to step in here and make a note that these differences also inform how the characters are built feat and item wise and how this differentiation is, at the least, similar to the differentiation in 3e, and at most much higher.
The multiple action types, and classes that get differing benefits from each type promote characters to seek out options to fill those voids where they have available actions. E.G. A fighter has a very strong immediate interrupt. However, if they're playing a build that is focused on AoE attacks to generate lots of marks, any time they use an immediate power they lose their strongest control tactic, the combat challenge immediate interrupt. This means that items which have immediate interrupt effects and powers that have immediate interrupt effects are much less valuable to them.
On the other hand, fighters which specialize in single target damage attacks will have much fewer marks going around, and after their marked enemy has made an attack, they are free for the round to use interrupts without ridding themselves of their primary advantage[since its already worked to make the enemy attack them, or at least, not attack an ally].
So in this way, the build of the fighter informs their feat and item choice to some direction away from immediate powers.
Its the same for the assault swordmage in various capacities. However, the swordmage cannot use powers for his attack that will prevent the other guy from dealing damage as the fighter can[free action item powers that land on hit and stun/daze/whatever], he can't do that because they won't prevent anything since his attack is a reaction. He is also heavily invested in minor actions as well, since his mark is an action. Paladins are in stark contrast to these two classes reliance on immediate abilities since it requires no action to trigger their bonus damage or protection, however, since the mark is a minor action they have the same hedging away from those.
However, both of these characters are move action light. Fighters because they can often charge[+1 attack/damage is nothing to sneeze at, and if the specific benefits of the fighters at wills are not necessary then its explicitly better than moving and attacking], swordmages because they don't need to to ensure a mark is set and useful. Paladins on the other hand really need their move actions or they need to ensure that they have ranged powers[which they typically do not], since they have to both use a minor to mark, but must attack or be next too the target to make it actually work. This is a minor action and a move action. Once their out of ranged attack powers they will need a ranged weapon and if that is the case they will either need the feat quick draw or they will have to burn their move to draw and attack.
With the mage, the mage is very likely dependent on sustain effects for maximum efficiency[at least mine is]. And that means two things, it means that they are very prone to being stunned or dazed and any ability that lets them pre-emptively remove these abilities. Loading up on minor actions isn't very valuable because they are going to be using those to sustain powers. On the other hand, they have nothing but protection abilities to fill their immediate repoitoire with. Alternately if the wizard runs with more save powers, they will not have these minor actions to use up and so minor action abilites are good fills.
Immobilize powers, which really really hurt the fighter, do almost nothing to the swordmage, and dazes, which really hurt the wizard, do comparatively little to disuade the fighter. They prevent his CC, but if he is adjacent he can attack anyway, and if he is not, he can probably charge.
This isn't even getting into the interactions between classes. When a rogue is around a fighter, it makes sense for the fighter to be heavily investing in push, pull, and slide powers. But without the rogue this is much less important, since protecting the rogue is not as much of a concern if your flanker is Paladin.[the push/pull/slide powers allow the fighter to get out in front of the rogue so the rogue can flank without being surrounded]
As well, that same rogue has an incentive to be heavily invested in charisma(and be a artful dodger), in order to diliberately draw OA's from marked enemies and so trigger the fighters combat challenge. Since enemies do not know its hard to hit the rogue when its provoking an OA, they are more likely to try to get the free hit in exhcnage for the CC than they would be otherwise. They might figure it out after a few swings, but there is no way they are going to know that halfling is an artful dodger rogue with 18 starting charisma and defensive mobility[total of +8 against OA's at lvl 1, combine with leather armor and the -2 from the mark and that makes a base AC at level 1 of 26. To compare a level 1 soldier is going to have around a +8 to hit, for a total hit chance of 10%, and the advantage is only going up as the players levels get higher and he starts adding more charisma and defensive feats]
This is of course, only the tip of the iceburg provided by one of a number of class and power combinations that lead to both wildly different and more or less equally valid combat strategies as well as wildly different and more or less equally valid power, item, and feat strategies.
