A warrior can choose to fill his entire skill bar (or atleast the slotable part of it) with signets but he can’t do so with other skill types, why the diffference?
In my humble opinion it would be nice if all skill types had at least 1 healing skill, 1 elite skill and 4 utility skills.
I know Anet is working on adding new skills and this would be a better first step than adding new skill types I think.