Just had my third attempt at GG Engineering as fire mage. Wiped at 90k cus I cancelled my ice block in a bomb, GG me.
Spec for NT - does more damage on this fight, try to multi dot but don't go out of your way to do it.
Spec for Cold Snap, pop your first Ice Block on top of Bo after the first shield, so all the rockets hit her, takes off a good chunk of the HP.
After this stick to Bo at all times, even when she is in the shield, Dragon Breath her, Deep Freeze her, do anything yo can to lessen the amount of lightning spams she gets out.
Pop Cold Snap when you get to 50% hp, and use your second Ice Block as soon as Hypothermia fades, very important you do it on top of Bo and not while she is under the shield. If she is not dead after this you are basically boned, but it is doable with 70k+ dps.
Speccing for Ring of Frost and getting them both stuck in at the start helps immensely for that AT/Pyro - combust opener, getting it spread on both before they port away is probably the win or lose moment. Make sure you are spec'd IW and use that + IB on cooldown, even with lots of control Bo's lightning does a fuckload of damage.
If you stand in any of Max's rockets, you lose.
Very hard boss for a class with extremely little self healing, but doable.