So about DEX scaling...
I feel that if you want to go with a pure DEX or DEX-oriented weapon (E/B scaling for example) then instead of getting to 40 DEX you should just meet the base requirements to use the weapon, infuse it with Raw, and then drop the Ring of Blades +2 on it as well. If my calculations are correct, this should give you ~40-50 fewer points of damage than a 40 DEX build, but then you'll have 25-30 levels that you can put elsewhere.
As an example of good DEX scaling, let's take a look at the Great Scythe from Dark Souls 1. At the base stats to use the weapon (14 STR/DEX) you would do 305 damage, the base 250 + 55 from scaling at the base stats! At 14 STR and 40 DEX the scaling damage goes up to a whopping 224, bringing you to 474 total damage! That's definitely worth the extra points into DEX.
In Dark Souls 2 the Great Scythe deals 250 base damage and at 16 STR/DEX you gain an additional 42 damage from scaling. Not terrible, a bit lower than the first game but it's still OK. Boost your STR and DEX to 40 and that 42 turns into... 84! So it would be even lower if you only boosted DEX. A grand total of ~80 points gained for a DEX weapon with A scaling and 40 points into DEX is a bit of a joke.
The same goes for Magic (Faintstone) infusions, the amount of bonus damage from having 50 INT is not very high at all compared to say, 18 INT (The amount required to use Crystal Magic Weapon after you have used ten spices on it). I am not certain if Dark, Fire, Lightning or Enchanted suffer from the same inadequacy as I didn't test them.
So in short, you can have a powerful build with low DEX because the scaling is quite poor. Put the points elsewhere and perhaps consider a hybrid build with buffs and magic on the side because you'll do a lot more damage that way.
Edit: Also, not to do with scaling but I'm still finding heaps of PVP and co-op at Soul Memory 7.1 million.
