Actually there's even more flexibility, since you can switch weapons in the midst of combat and completely change your first 5 skills on-the-fly or as the situation warrants. Sure, you can only set the last 5 skills, but you get more skills to play with in combat. And there's traits that change how skills work. Also, certain classes, like the elementalist, have access to even more skills on-the-fly when changing attunements etc. Oh, there are 10 skills in GW2, not 8.
It's not that drastic as it may seem at first. :)