Aside from that, I noticed you're not utilising your procs for movement. As result, you'll have a bit of down time when you have to hit the towers. From the video I conclude you have tower duties on set 1 and 3. I didn't see set 1, however.

What you could do:
With set 1, stand in the outer ring of the tower circle (not in range to trigger, but in range to get the debuff). Have someone else trigger the tower for you. You can safely loiter around the tower, as long you're not triggering it. When you get a firestarter proc after you get your stack, use that proc and move back to the group (you can't cast anything anyway after the insta fire III)
With set 3, wait for Ballistic missiles. When you get a proc at this point and you're not bound or have to stand in there for the missile, use that proc to move towards the tower range again, loiter around and wait for proc. Same as set 1, actually.