HUMM......urr.............right.
1. I've always found that the harder the setting on the Sathanas mission, the easier the turret mauling. Maybe it's my imagination, but your Helios rip a much bigger damage on harder levels of combat, so essentially, all you have to do is shoot the beams four times for them to die (double launch of course).
The way to get the fighters off your back is to c38 your wingmen a lot, and the way to get the flak off your ass is to Treb it (you don't start at 9000 for nothing) and for the other flak cannon, to have support on your ass at all times (it tries to dock with you, but you keep moving, so it's covering you.)
The Demon itself is easy, and you don't need wingmen for it. Again, since the damage values are higher, what you do is you kick it's beam cannons with your trebs, and then nuke it's engine with one salvo of well aimed Helios.
The pain of this mission is getting all those variables to work properly, but it's possible, and not _that_ hard.
2. The Hinton/Iceni mission. Urrrr......I'm sorry, what's so hard about that one? I mean I've never had the waypoints for them to collide (actually maybe I did, but I didn't care), but all you have to do in that mission is kill Sekhmet/Bakha first and Tauret second. I think you can take a ****load of tempests in that Herc1, and the guns on it are spectacular enough to take care of anything that strays (like them asteroids).
3. Tiamat one. Yeah I had a lot of grief with that one until I figured out the same thing as the first thing. Beams deal a lot greater damage on higher levels of difficulty (again, maybe my imagination, but I just found it to be true). All you have to do is make the Tiamat in your sensor range as soon as it jumps in, and take out it's two beam turrets when the fighter/bomber Shivan salvo is resting.
After that, you can try to keep close to it, but I just prioritise little ****ers and let Aquitaine do it's job (it always does).
Hurrrrrrrrm............yea.