I've been thinking this over a bit, and decided to take your advise and drop Dervish.
I've been a bit hesitant about x/day abilities anyway, and the main reason to go for Dervish was to get both movement and full attack, which is also possible by obtaining Pounce.
So, I've changed my build to:
Human.
Barbarian 1 (Complete Champion ACF Totem: Lion replaces fast movement, gain Pounce ability)
Ranger 4 (Complete Champion ACF additional feats replace spellcasting, Player's Handbook II Distracting Strike replaces animal companion)
feats:
1: Expeditious Dodge(*), mobility
3: weapon finesse
6: spring attack
9: Improved Skirmish
scount 4
4: Swift Hunter
ranger 4/additional feats
2: two-weapon fighting
4: improved two-weapon fighting
(*):Expeditious Dodge, from Races of the Wild, gives you a +2 Dodge bonus on ALL enemies, but only activates when you move at least 40 ft. It can be used in place of the Dodge feat to qualify for a feat, prestige class, or other special ability.
I'm planning to take greater two weapon fighting at lvl 12, although I'm still moving some feats around a bit.
I'm also planning to take the Tempest Prestige Class, but I'm still not sure when. If I take another level of ranger, I get another Favored Enemy, a Favored Enemy bonus increase and, because of the Swift Hunter feat, another d6 skirmish damage.
With two levels of ranger, I get another combat style feat, which would get me Greater Two Weapon Fighting a level early.(and get me another favored enemy and favored enemy bonus)
Taking another level in Scout instead would get me another d6 skirmish damage, evasion and, because of the swift hunter feat, another favored enemy and favored enemy bonus. In exchange, my BaB won't improve.
Two levels of scout would get me Flawless Stride. Which might come in handy when a lot of your build depends on being able to move. (and get me another favored enemy and favored enemy bonus).
(Sidequestion: does this ability allow the Scout to charge over difficult terrain?)
Basically, my question is:
What are the 'sweet spots' of the ranger/scout build with swift hunter?
I could, of course, keep taking ranger and scout levels until lvl 20, but I want to get into Tempest at some time. I just want to minimize the loss from dropping the ranger/scout progression.