Honestly, it seems that you're doing fine if those are your 5 man dps numbers. 2500 is a little low, but anything 3.5k+ would easily put you in the top 10% of players in 5 mans.
Heroics are a terrible way to get your real dps numbers. There's entirely too much variation from group to group, giving you huge differences in buffs, kill times, and everything else. I wouldn't give too much weight to the recount numbers you see while doing them, just as long as it's not absurdly low. Had a 4k gs dk do 450 dps today, it was terribad.
Most classes in random groups will do less than 50% of the dps they can do in raids due to those issues, but they'll have huge spikes on occasion as well. I've done 10k on bosses in heroics on my rogue, but that's far from the norm.
I've never seen anyone sustain 5k or higher through a single heroic, and it's pretty rare that you get anyone over 4.5k. Generally see someone sustain 4k about one of ten heroics maybe. I generally hit in the high 3k's, breaking 4k when kill times are a little longer or there are a lot of aoe pulls. Did have an awesome heroic the other day that all 3 dps were doing over 4k the whole instance though, that was pretty great.
I generally just expect people to do dps that's somewhat in line with their gearscore. The gearscore does grow faster than your dps numbers though, by a small amount. If your server is big on this addon like mine is, it's something to watch, you should see trends in gs vs dps pretty quickly.
*edit* to give you a better idea of where I'm at,
this is me.