The main problem with doing a LD yes/no system is that there's no forgiveness or opportunity for the Eldar player. It's simply "phew, my ship can't get shot at by his 16 gun Carnage" or "Oh my god, my Void Stalker is dead because that stupid Locked on Carnage scored 10 hits" There's no parity in a system like that. And it means that players who rolled well on their LD or players who have built a lot of LD over a campaign will wipe Eldar MMS players.
I completely understand that some people would hate shields on Eldar, but it's really the same story with MMS or MSM. You keep your fleet together, putting your long range shooters in the middle. You deny them sunwards movement as best you can, and you shoot the "holy and esteemed lord christ" out of them as soon as they come to shoot at you (or sooner, if you've moved properly).
Look, WB's suck one way or another. The total damage you can inflict with them is piddly compared to lances, torps, AC. They were only good for fighting MSM eldar. So for the sake of a campaign, there's no reason why players should be complaining when their lances, torps, and ord (most likely their main weapons of choice) are so much more effective.
I would much rather have my lances hit well against all my enemies than have to spend a bunch of points on crappy guns just to fight MSM eldar.
The folks who hate Eldar shields most likely long for the days when eldar ships would get destroyed by blast markers. The fact that you can even shoot at Eldar with MMS balances the game so much that people should be dancing naked in the streets. MMS Eldar have to engage at 30 cm, which leaves opposing fleets tons of room to work with. It practically guarantees that you're going to be able to pull off a counterattack provided you're a good admiral. In order to be fair to Eldar MMS players, it's almost a necessity that their ships get shields. They're significantly more expensive to field, which means less total hits on the board than any other fleet. They no longer get to turn 360 at the start of their movement (so their capital ships will almost always be privy to taking a few shots).
You shouldn't debuff shields for two reasons. The days when a squadron of escorts could be destroyed by blast markers should forever be behind us. And if you lower the amount of shields capital ships have, it'll just encourage escort spamming, (which will aggravate slow turning players even more).
One thing you might play test is having no right shift for shooting at Eldar. Your holofields rules on lances should then apply to all DF weapons, (I feel it should also apply to NC, as not incorporating this gives IN a big, juicy boost.)
Or, give Eldar players something like "weak shields" on top of holofields. Mostly normal shields that fail and let the hit count on a 5+ (or something, find a number that works for you) This would give you a 2-shield average for a Void Stalker or Wyrm.
All I can really say is that if people would rather go back to the days when Eldar fly in, waste your fleet, and then fly behind you where you can't shoot them, then be my guest and go back to MSM Eldar. But I've fought that navy and I never want to again. So you can't have it both ways. It's up to you, as a player to develop the best ways to deal with the fastest moving fleet in the game. And really, it's so much better for you that now they have shields instead of you being completely unable to shoot at them. Nerfing them won't change the fact that you're not a good enough Admiral. The GW BFG champion 2 years in a row fights with Tau, not Eldar. I'm sure you can manage just fine.
