Is this single target DPS vs say the Heroic or Normal target dummy?
Is that with buffs from the group for each toon, or running solo?

I'd imagine 25k to the Whelps in Onyxia would be relatively easy for a raid buffed AoE toon, but a lot harder against a solo boss, especially with less than full raid buffs.

I don't have Shammies at 85th or Mages, so cannot comment on either really.