"And we wouldn't gotten away with it too, if it wasn't for you nosey kids and your stupid shock combos" <shakes fist>
Well, I think one of the main things that we've all improved on is power up timing, and I think that's mainly because a) we're starting to memorizing the timings and b) we're communicating better about the timings. And communicating better also helps when it comes to sticking together as we move through the map.
A couple thing as a group I think we can work on is moving around the map to flank the opposition (looping around a corridor and coming up beside/behind an enemy while they're pre-occupied with your teammate; keeps you from shooting your teammate in the back by mistake

) and covering your teammate's escape when they're caught in a 2-on-1. We were doing some of that today in practice but we can probably do more/do it smarter.
Personally, I know I have to work on using the shock and shock combo/avoiding same. I stick mostly to flak/lightning/rocket launcher because they're close to each other on the weapon wheel, so I don't get down to the shock rifle much (I know, I should bind a key for it

)
That, and keeping better tabs on my health AKA knowing when to run away/not pursue somebody and get health instead. As Kraniac/Landslide pointed out before, TDM is as much about staying alive and not giving the enemy a frag as it is about getting your own frags.