Tiers for Skills
We’ve organized each profession’s elite and utility skills into three different tiers, or levels. When you get enough skills in one tier, you unlock the next level of skills. Why the change from the previous model, which let players choose from all the available skills at once?
“The tier system gives players both a sense of progression and accomplishment,” says Lead Designer Eric Flannum. “It encourages them to experiment with different skills as they increase in power, and it avoids overwhelming new players with a huge list of skills to choose from.”
“Plus,” Flannum adds, “the tier system is more scalable and expandable. We can more easily add new skills in the future with this system.”
http://www.arena.net/blog/the-big-beta-weekend-preview