Perhaps some are jumping to conclusions...
The assumption seems to be that Eldar ships are made mostly or entirely of wraithbone. This seems to not be the case. Wraithbone is only one of the psychoplastics Eldar use and fluff states its the most unusual (Eldar codex). Fluff also states that Eldar ships are fragile and not capable of withstanding bombardment and rely on holofields to protect themselves (BFG rulebook). They must just be using wraithbone for specific parts of the ship and other psychoplastics for the vast majority of the ship. Can anybody site fluff that Eldar ships are made of wraithbone? Can anybody site fluff regarding Eldar ships being well armored or otherwise extremely resilient?
The fluff does state that wraithbone is tougher to damage than adamantium, but we are talking about plasma torpedos, macro cannons and lances. Thats a lot of power there that may be able to damage adamantium fairly easily.
Besides, a ship that is out of damage points means it can no longer fight for whatever reason, not that it is completely destroyed.
Smaller crew could mean lower crew density. It could also mean crew losses have a much greater effect on ship operation.
Damaging wraithbone might have a huge disruptive effect on ships systems. A ship made entirely of wraithbone would be able to rerout power and comms easily, but if its only a thin frame inside the vessel, damage could potentially shut down whole sections of the ship.
What do we make of Dark Eldar ships which have no access to wraithbone?
Decades of precadent in rules and quite a bit of existing fluff describes Eldar technology as sophisticated yet fragile, and shows that Eldar prefer speed and obfuscation to heavy armor. I can't see a viable argument for Eldar ships having 6+ armor. I don't think fluff or precedent supports it. And I don't think the game can bear it.
Ah, I see now. Ships can position themselves to avoid closing fire. So, why can Eldar do it, when they turn 90 at the beginning of a move but chaos escorts can't when they can turn 90 at any point in their move?