Its an interesting argument I was having with a friend of mine. So far in our experience, all of the core roles seem to be able to put out good damage...with the exception of the leaders.
Striker - Of course
Defender - Fighter - Lots of multi attack powers with high W's lets him put out respectable damage time and time again.
Controller - Wizard - Wizards get lots of crits due to their area effects, and several of their dailies are actually very strikerish in nature (flaming sphere, bigby's icy grasp).
Well, I think the base premise being presented here is something of a faulty one. The Fighter is typically good at dishing out damage, true - but that is largely due to the Fighter having Striker as a sub-role, and thus more easily stepping into those damage dealing shoes. Other Defenders can certainly build for damage as well, but not quite as easily - and the same goes for every class, including the humble Cleric. I certainly think the laser Cleric can compare well to the Wizard - they have plenty of their own dailies which are pretty potent (Spiritual Weapon, Blade Barrier, etc).
In general, many Leaders and Defenders and Controllers will do around the same amount of damage. A sword and board fighter, a paladin, a wizard, a cleric, druid, shaman, bard, warden, swordmage, etc, etc, etc. All these guys are going to tend to be in the range of 1d8+Stat+StandardBonuses for their most common powers, and then have some fluctuation in encounter and daily powers, but usually staying in the same range. Assuming those builds focus on emphasizing the specialties of the roles - Durability and Enemy Acquisition for Defenders, Healing and Buffing for the Leaders, Multi-Targeting and Disruption for the Controllers - then the damage between them will all be pretty comparable. It will all also be lower than the Striker, of course - how much lower depending on how the Striker is built, and whether it has focused on its own specialty or on branching out to other roles on its own.
Now, you can also take any one of those non-Strikers, and have a damage-oriened build for them. I'd say this is possible for all of the classes, though some certainly have an easier time of it then others (such as Fighters.) Any Weapons-based wielder will actually have a bit of a boost due to the potency of Superior Weapons (AV2 might do the same for everyone else when it introduces Superior Implements.)
And for anyone, the option is usually there to focus on powers that grant multiple attacks, that can be sustained for more damage or to repeat attacks, powers that attack as minor or immediate actions, powers that hit multiple foes or are hard for enemies to avoid, etc - while also snagging damage-oriented equipment and feats - can allow you to find a build for any class that will do decent damage.
Now, a Striker that is also focused on damage will almost universally come out ahead anyway - but I don't think any of the other roles are gimped in comparison to each other. But it all depends on build - and, generally, sacrifices will need to be made. A cleric built to deal damage won't provide as much healing as one focus on healing. The damage-cleric might still have
enough healing for the party, of course - it just won't be as much as they could
potentially bring. In some cases that won't be an issue, in others the difference will hurt.
Which is fine - that's the point of the game, making decisions matter. Both builds contribute meaningfully to the party - that they contribute slightly differently is simply evidence of the strength of the system.
