Vorkath 6 Minute Kills pls help

Good afternoon iron friends

I can't get this dragon to go down at any relative speed and end up using up all my resources. I could use my brews but for some reason I'm being stingy on them.

I'm relatively new to PVM and definitely enjoying it but 6 minute kills are driving me a bit mad. I only have 84 range, and clearly RCB and no archers ring is causing issues accuracy wise - But i can just never hit ruby specs, when I did I got my PB of 4:34...