Let me give you some advice: Wear them down until you can kill them both in a single blow. Then, use a shield and fire off a multi-strike technique to take them both out.
Be aware that the boss follows a pattern of sorts, with the seek and destroy ability, prep and react in kind, shielding yourself before it can stun you. If stuns you and uses the breath weapon, you're in for a galaxy of pain.
If you only kill one, the Dragonoid gets a REALLY nasty power boost and can kill you easily. Take them down, then UNLOAD on the boss. Keep it blinded, stunned, or a shield up whenever possible, and make sure you have some sort of healing or life-leech skill, stack on DoTs, hit it with Criticals. If you have anything that triggers on golems, use it, if you have a really powerful weapon of any element, use it.
Sadly, my ultra-easy quick and clean method that I use on the other ones doesn't work on this joule-jerk. But the outlined method here is about as good a was as I have found to end this mechanical nightmare.
Basically, you just need to keep a guard up and keep your health high when the little mechs are alive, drop them at the same time, then disable the boss and just tear it limb from limb.
Done properly, you can get it down under half-health in one go.
Pet dragon is a good companion for you, too, it can heal, stun, apply DOTs, and inflict chip damage on gruesome over there.
Best of luck, this is the best advice I can give you.