I've never had a problem with the eldar. Fighting them sometimes can be very frustrating but I've never felt that I didn't have a fair chance at winning. If I had to pick a broken aspect, or maybe just a mechanic that is unfun, I'd go for the 2+ save on the Necron fleet. You can set up the perfect attack and if he doesn't roll any ones its all for nothing. On the other hand you can play like a child and if he rolls lots of ones he'd most likely lose. I guess everyone's milage will vary. I think that a lot of a person view as to the flaws of the game will come down which fleets you normally play against and how good those people are at the game.
Okay,
Eldar official rules.
1] Move, Attack, Disengage
surprise attack or similar. 750 vs 1500pts
Turn 1 movement: Eldar on board
Turn 1 shooting: Eldar destroy ship(s)
Turn 1 ordnance phase: Eldar mop up if shooting wasn't succesfull or destroy more.
Turn 1 end of ordnance phase: Eldar move fleet of table.
Opponent nets 75vps, Eldar net destroyed vessels (> 150).
A daft Eldar win with no play for opponent. See, no cool player would do that but Eldar rules make it possible.
2]
The Volandum ManouevreLock on with Hemlocks (boom boom Pulsars!) (lock on = cannot turn in movement + ordnance phase)
Fire torpedoes (str2) at Hemlock squadron.
Hemlocks Brace for impact!
BFI replaces Lock On. Hemlocks may turn and move at end of ordnance phase.
Totally gittish but rules allow it.
3] Necrons are blamed for Eldar losses.
Wrong, Eldar loose because of Eldar rules.
4] Fluff
Wraithbone is stronger then 4+.
The most advanced race has no protection against space debris. Being arrogant is one thing, being a stupid race another.
The most advanced race has almost no protection vs the most common enemy weapon (weapon batteries). 1 dice from a mon-keigh ship can kill thousands of a dying race @30.000 km away. 1 dice on a 50% chance.
Again, a dying race may be arrogant, but stupid?
The problem with Eldar rules is not that they are too strong or to weak (funny enough they are too weak and too strong combined!) but that they are broken/badly written.