Given that you say 10+ damage phases it would seem that you’re not getting optimal damage each phase. Your Taipan has firing line which won’t help you as you have no allys. Also try using surge mods that match your heavy. Yes it did take me over 3 hours to actually finish my solo run (ecthar was my nemesis) & I do agree that the health of both bosses is a little extreme but you should still be able to enough damage to final boss in around 6 phases. If you made it all the way then it’s definitely worth trying again & you’ll probably find it won’t take as long next time.