When you are first able to have two auras, you get Keen Observation, while being able to cast Vim and Mystery. It's a very very clear choice with what should be that second aura. The first sometimes too.
How about making buff like Wind Warrior, Fire/Air Shield, Buffalo and any other buffs like that, have their effectiveness scale with a players level instead of being an absolute amount? This could help prevent low level players being able to advance levels too quickly by letting the 'buffs do the work' to kill stuff for them.
Whoa whoa, what's with the hate on the transmog game? Not cool man. Not cool. In any case, what you're suggesting won't really fix things, since any transmog'd class can have fire shield, wolf/buffalo and WW...and then cast this buff on top of it. So you're still helping them anyways.