This was discussed earlier, but if you can help me get more specific than "a few hundred dps" when calculating the value of the proc, I'd be happy to toss it into the crapsheet. Well, that, and if anyone can point me to the EP value of DPS assuming T14 BiS.
According to comments at Ghost Iron Dragonling the dragonling proc will do about 13k damage per proc with a cooldown of roughly a minute. One poster said, he tried different gearsets and the damage of the proc didn't change, so its most unlikely to scale with gear.
One of the earliest MV logs of my raid show four procs on a 6:10m fight, doing 720 dps while it was active with 55295 dmg total over the course of the fight. Thats ~13824 per proc which confirms the statement on wowhead.