I agree that 5k honor per hour seems a bit high, but 3k honor per hour is certainly feasible from stone keeper shards.

I pull that on average from slogging through heroics with my DK+4ret team, in ilvl 232+ gear, and that is with full trash looting.

Once you are geared, you will be shocked at just how fast you can rip through heroics.

Seal of Command + Divine Storm "blender of death" on gathered up trash packs, and Seal of Vengeance/Corruption on bosses. Both trash packs and bosses go down in a handful of seconds with little to no direct healing required. You can just basically steamroll through non-stop.