I understand your point. However my point in of view is that the first design iteration of anything is rarely (if ever) optimal (and it can be argued that with SE they made AST worse with further releases). So just because something was designed , or has specific functions in its first design typically doesn't mean that it won't have changes in future, so nothing should be sacrosanct - especially since we only guess at some of the reasons for SE design decisions.
You haven't convinced me AST should only have 2 DPS abilities (note that I'm not constraining that to buttons)- I fully agree with ASkellington, it may end up with the least DPS skills but the current overused 2 is definitely lacking in engagement.