I have a very strong opinion when it comes to the eldar. They are not represented as a superior race and they should be. They are a dying race. They save themselves in soul stones when in battle. What happens to the souls that are blown to smithereens by being on a lightly armoured ship? To me it just not make sense. Light armour on a pirate fleet I can understand. Speed and armament must come first. On a battle fleet however, armour should be available. Should they be as heavily armed or as fast as a pirate fleet? Hell no. This is not their raiding fleet but their defense fleet for their craftworlds.
Besides "These are Eldar", give me another reason for them not to have better defenses than any imperial vessel IF they are so technologically advanced. I recognise the need for game balance, but this is where points come in and limit the eldar from fielding a large sized navy.
In short Eldar should be limited in number, but almost unlimited in every other regard. This is what technology gives your forces.
The armour 6+ on the front is demanded by the range of their guns and turns. They must face the front. Have a good look at the model and tell me if it looks like it couldn't take more damage than a SM strike cruiser. I'm not asking for them to be impossible to kill, but they should be harder to kill than they currently are but that being said, they should also pay for it in points. The 6/4/5 would suit their playing style.
I'm not asking you to agree to this proposal but to think about the changes to the Eldar from MSM. The MMS Eldar are no longer the terrain huggers their forebearers were. They need new thoughts and insights to allow them to evolve into an enjoyable and challenging fleet for both player and opponent.