Defenders can have a quite helpfull Damage! And help ( and a lot ) is the main thing here.
1. Of course there is no sense in comparing dmg with a buffed blaster or vs a blaster attacking a debuffed target...
However ( in my case ), a Force Field defender.
1. I'm (still) stacking a TONS of global recharge speed + Force Bomb (w/+100 recharge Force feedback) .. I'm getting Thunderous Blaster each 25 seconds and I'm not even close to limit.
2. Defender have stronger Aim, Power build up (also spamming a thousands)
3. The (New) -Res debuff is quite good for him and all party Dmg.
4. Party becomes near immortal with 3 slots of IO only (for the two 'shields others' ) so Why more ? Go for damage lad!
5. Defender are pretty much hard to hit so .... Use REDs at will ..you will not need purples like blasters. (though will still need anti-stuns/CC and care about resistences)
6. Defenders are 16 Targets Aoes .. Just do the Math, if you are surrounded your total damage will be way more than the 10 or 6 targets from other ATs.