This would also be quite useful for some other classes, too. There are times where you have an open slot or two for x-class abilities. For example, if I'm offtanking on WAR, I prefer to have Mantra set instead of Flash (especially in fights where you aren't managing multiple targets). Often, I'll set Mantra but forget to go back to Flash for normal dungeons, and then I'm left with only Overpower. I like to balance between that and Flash in these cases. Similarly, I might not always decide to use Awareness (I mostly use it on high damaging targets, where a crit can potentially kill you - but in weaker fights, even a crit isn't going to do much).