i only play Arms spec as an offspec but looking at your gear, rotation etc i wouldnt expect your dps on a dummy to be much more than 3.5k
remember in raid environment you will be raid buffed and also using flasks, pots etc to speed up your haste/attack speed and AP. As such it wouldnt surprise me if in a raid environment you find on a static boss that you can easily pump out 4k dps with your gear level.
A few gem upgrades and bit more AP can make a big difference.
Also try binding heroic strike or OP to your middle mouse wheel and spam it.
In addition have you tried stacking 5 sunders then starting your dps rotations ?
As i said im not a pure arms warrior, so this is only what i have been doing myself, others here will know far more than me on achieving dps at 5k +