Okay, these are wildly different sorts of games. On the whole, I'd say DCUO is a tense button-mashing action game and CoH feels more relaxed and social. Nevertheless, I think these two games could learn a lot from each other. (Okay, DCUO has a *lot* to learn. Did they even play CoH?)
The best and easiest thing CoH could learn from DCUO is the way DCUO handles Badges. They call them Feats over there, but they are the same concept and earned in much the same way.
However, there are two notable differences:
1) In DCUO, each badge has a point value. Each time you score 100 badge points, you get an in-game benefit. (It doesn't have to be something as extreme as a new skill, but porting this reward system into CoH would be terrific.)
2) There's a special screen in the interface that tells you not only which badges you've collected but which you have not and what you have to do to collect them. All information is fully disclosed.
The combination of these two elements is terrific, as it leads you to proactively going on your own little missions and errands rather than just always running around at the whim of your contacts. (There's a lot of that in DCUO too.)
I would love to see this Badge point system introduced into CoH. It's almost there already.