from what i remember it was like 600 main, 200-300 offhand, now its like 300 main and 50-80 offhand 
Yep, there's also issues of CK not working properly. Damage is definitely lower than before. Another issue is that samurai cards do not work for soul break when in off hand.
Q1: What happpened? I believe that on Aegis they had a boost? o-o or something? and now on EAthena they changed?
Q2: Would it be possible to get this boost back?
Q3: Does Naght act like a Dagger SQI ?
Q4: What build is good for a good DPS dagger sin?
Link me or respond to questions please :O
I don't wanna hear about soul breaker sin~
You could try a naght sword build but your going to need to stat more agi to hit 190 aspd. You cant switch directly either, you will have to use a katar to de-equip both dagger and sword.
Plus, daggers and soul breaker go hand in hand. Not using soul breaker with daggers is taking away one of your most powerful skills.