In my experience cybie can be a bit tricky when you're going with a MaD build, since you block HR.
One tip for Cybie fight with MAD - set your tactics to running. With this, your reloading time is decreased (thanks to Shottyman), your dodge chance is increased by 20% (from 40% to 60% with only one square between you, and another +5% for each subsequent square), and shotguns don't suffer the accuracy penalty, so just run towards him and unleash your double or super right into his face. Even in a fireproof red, you still would fire faster than him. Sure, you'll probably have to eat a rocket or two, but even then, with this setup, you may as well not need even a single medpack.
And to the OP: Congrats on that GK Gold and the win. A bit of luck there, but sometimes RNG just works for you.