Why did FFG do that? (less than 10 cards in each type of encounter cards)

I think it's b/c, by making the encounter decks smaller, the encounter deck can really interact with itself. So, some of the Shadow effects pump up Type-X enemy - if the encounter deck was large, and mash of various things, that effect would be less likely to go off.

In my opinion, since the encounter decks are smaller, the game has gotten better, as the encounter deck has gotten "smarter."

But the setup up time gets longer and when i finish the game it take me more time to sort up each encounter deck.

I'm not sure how the encounter sets will be used in upcoming packs, but for now I think there is only one set that is used in multiple quests. If I remember right, Peril in Pelargir stands alone, and the second and third quest share the set with crossed arrows. Not much encounter deck prep is needed, if you just keep them set up. 

Like Dain said, the smaller sets work with each other more carefully and in my opinion seem to provide a more consistent quest.

Glaurung said:

Hmmh, but smaller encounter decks make the game even more predictable. Which is what I like, as you get a better grip of what you'r going to face. PiP is a good example, with only 32 cards and 5 cards that surge. In fact, the developers succeeded in reducing the encounter deck by cheating: they simply gave each enemy a forced effect that would ususally require its own treachery card.