Are you running the latest version of BP, not SCP? Up to date from Knossos or the installer?
Up to date from the installer, the Artemisia mission(not sure if i wrote that well) has a similar issue, whiout checkpoint its WAY too hard, and im talking about Medium, i cant imagige doing this on hard or insane.
And the reason of this is that the checkpoint is TOO GOOD, there is only 1 remaining remaining Serker corvette at very low hull that will jump out as soon as you drops it below 30%, this means, by the time the Diomedes jumps in, all ships in the are will start sending torpedos, this creates a distraction for AAA and point defense turrets that makes strikesa lot easier. Whiout checkpoint at most i can get 1 corvette to jump, 1, no chance to get rid of the other two, this means all allied ships will be keep shooting at them and not at the Diomedes.
For the Diomedes, whiout checkpoint, the same issue as before, use fighters as meat shield at the same moment i can get in with paveways, this way saturation strike and gunships can kill it. But at least i can do this because i have Paveways. I expended two and a half hours until i finally did it. You have to time everything right, and there is one chance to get it right. I dont know if this is intended, im a veteran player i can take the challenge, but seems a little to much to me. Specially considering the mission COUNTINUES after that, getting killed attacking the awacs after that will result in several insults.