There is no "heroic" training dummy as far as I know. Only the level 80 and the "grandmaster's" which is 3 levels above you - like a raid boss. Heroic bosses are only level 82. Your hit is only 109, which is fine for heroics but not hit capped for raids. You are probably missing quite a few casts.

Your gear and dps for this dummy look fine. What's the problem? The training dummies are there for you to compare the relative efficacy of rotations/gear for yourselves, not to look at your DPS against someone elses parsed data under raid or other conditions and make any kind of valid comparison.

There's a lot of e-peen waving of DPS numbers, but unless your comparing apples to apples I wouldn't pay a lot of attention to this. Raid buff/debuffs and multiple targets have a huge impact on these numbers.