Normally, the success of a group isn't measured by how many enemies they beat, or how good the XP per hour is; merely how fast the team perceives itself as moving through spawns.
Don't get me wrong. When I'm gaining multiple bars of XP per mission, leveling more than once with the same group post lvl 20, yeah, that group is badass. However, in general, the teams I remember most are the ones on which I felt like I was unstoppable.
Now, as awesome as my Blaster (Police Drone TH) is, he is made stronger by good teammates. Specifically, Tankers and Defenders.
Now, this isn't some post extolling the virtues of the "Holy Trinity" (Tank/Healer/Mage). Instead, I'm saluting the people who control how fast the team rolls. In CoH, it's the Tankers and Defenders. Tankers who eat alphas and manage agro, and Defenders who buff (not heal).
Tankers get a bad rep sometimes. They can be regarded as glory hounds, or seen as trying to do all the work just to show off. However, the real strength of a Tanker is in his ability to embolden the team, and make them strike harder and faster, having faith in the Tanker to keep the agro off them while they rain hell. This applies equally to all classes, not just "Mages". It's safer to debuff once a Tanker has moved in. It's safer for a Scrapper with a mandatory agro aura to engage the foes. Additional agro is less of an issue if the primary spawn is being adequately managed. Tankers, when performing their job properly, help set the pace at which a team does it's job. The better the Tanker, the faster the pace, without team safety being sacrificed.
Any player can tell you that they feel much stronger when an Empathy/Thermal/Pain Manip/Kinetic/etc buff is cast on them. The very nature of buffing powers in CoH lends huge strength to a team. Strong characters are bold ones, and a buffed team is more confident going into battle. While they may still be numerically inferior, they will most times still press on, putting faith in that extra +18.5% def the Defender gave them, or the extra +500% regen the whole group has. Knowing that they are backed by a vigilant Defender (no pun intended), a team is more likely to stand it's ground when people start to fall. More likely to keep fighting when they would otherwise run away. I've seen more team wipes resulting from premature retreat then from failing to run away fast enough.
When solo, I know my own limits. I can ride the razors edge, and tackle odds far greater than most other players. Most players perform better when solo, as they only have themselves to consider in any given situation. When teamed, everything changes, because up to seven other people can be impacted by what you do. When teamed, I have to exercise restraint, since more than my own fate rests in the balance (and usually, the odds are vastly stacked against me). However, when teamed with the right people, when there is the right combination of agro management and buffing, I can once again become the engine of death that I know I am. And this applies to the rest of the team as well.