Hi, damage from the weakest double helix 10 is 2 x 30969 =  61938 ; Add double damage 2 x 61938 = 123876 ; also add damage from pilot (lets say 9.5%) = 135644 and also from implant. Some missiles might have hit you from sides and from behind, which also increase damage. Sheeld? Useless. Bastions sheeld protect sides and not top. Helix hits from above.  

It sounds like you encountered a weird issue in the game, and you're right to question it. With Bastion's 130,800 HP plus the 27,600 bonus, that Helix Rack 10 damage shouldn't have been enough to take you out. Maybe it's a glitch or something thelrapk —perhaps a hidden factor affecting your health.