I have mine set to per combat and only keep Boss segments. Never cared for Overall, it just doesn't tell you anything useful.
Anyways, 10k is low and really does show that person is either geared wrong, or not playing 'correctly' because all this I see about low HP trash packs being an excuse is BS...
1. This is ZA/ZG, the adds either have a LOT of HP or,
2. for the many of the pulls with low HP add, there are a lot of them so searing is an option.
I was one of those people doing 10-12k the instant I hit 85 and got into heroics (but I wasn't in all blues either.) And I was geared appropriately (stacking Int, haste, and spirit.)
Examples where I've seen HORRID SPriest DPS/play:
1. very liberal use of mind spike (doesn't understand mechanics,)
2. basically Mind Searing only, even with 1-2 mobs (plain laziness,)
3. geared in healing gear (reasonable, I have asked why are they queing as DPS: 'not ready to heal this yet,')
4. Full PvP gear (1-4 pieces I'm ok with since I do it myself, but PvP everything, even trinkets too?)
5. not dispelling mobs (doesn't lead to low DPS, but it annoys me as a SPriest that they don't make use of it.)