The point was that the Osiris doesn't suck. You can argue that the Amun is better, but you can't argue that it isn't an effective design as long as you have an AI that can actually use the turrets. The Sekhmet is probably a better ship for the player, who is actually able to defend itself, but the Osiris is gonna give you more trouble in tight wings.
We had to nerf the bomber turrets in BtA, reducing rate of fire and giving them fov, just so they wouldn't be completely, utterly overpowered. And even after that, they will still run their own escort, and don't expect take them out alone and without damage even with a fully armed Herc.
Survivability-wise, Artemises and Boanerges are just ridiculous jokes compared to Osirises. They're just flying targets. Osiris is a flying gunboat.