You're quite right. In the normal game, damage auras tend to contribute a lot of damage due to their passive, always on, AoE nature. People who've watched it with data tracking software reported numbers in the 20-30% range more often than not.
In the highend game, as characters plow through groups faster and content gets more dynamic, at least the kind of content much of the playerbase seems interested in running (itrials and speed TFs), burst AoE gets more important, but damage auras remain interesting.
It's not a 'big' thing, but it is a noticeable one. A brute with a heavy single target primary and a damage aura will take down a large enemy group faster than one without. The trade off is that sets without a damage aura tend to be among the more survivable ones (there is one glaring exception to this, however - Stone Armor has both a damage aura and massive surviveability in granite, though it pays a hefty price in damage output and combat maneuverability for it).
At the end of the day, though, the AoEs you pack are what get the job done. Both my Stone Melee/Willpower brute with Tremor and Dark Obliteration and my Superstrength/Fire in all his aoe glory, including the damage aura, waltz through x8 paper/scanner missions in 10 to 15 minutes - most of which is wandering around the map time. Outside of ambush farming there's really not a hell of a lot of difference.
Weight training: Because you'll never hear someone lament "If only I were weaker, I could have saved them."
Yeah if you choose one of the sets with the damage aura's then you do need to choose it at some point to finish the fights quicker so you don't take as much damage. If you choose a defensive set you are more survivable but fights will last longer.
On my SS/fire/mu when he farms its his 3rd most dmging attack over time, taking AoE into account. So it beats out burn and electric fences.
In content they still kick ***, as they tend to put out roughly 10-15 dps on the low end. I find that they really shine when soloing AVs
As Nihilii said tho, in faster paced action they are less useful.
"I have ridden the mighty moon worm!"
-Al Gore
Fiery Aura is only good for farming, I'm cereal
@Caucasiafro
Even in speed content at some point you get to a hard target that slows things down and it's a free 10-30 dps.
In trials you don't get quite as much out of it due to needing to move at times but I'll take all the animation time free damage I can get my hands on.
Global: @Kelig
Thanks for the replies!
The trouble stemmed from me wanting a Natural Origin samurai-themed brute with Katana and me having trouble fitting the damage aura sets into that.
But I feel that I really want one of them, especially after reading these replies so in the end i took /fire, colored it blue and said her fighting spirit is just so strong it manifests itself as blue fire, hey, it works 
Hey all.
I've mostly been playing ranged characters and have decided to try my hand at the Brute AT.
Basicly, about how much of your damage comes from the damage auras if you have one of those sets? From teaming with brutes, those auras seem -really- good, but at the same time I'm more drawn, concept wise, to the other defensive sets which lack the auras.
I'm especially drawn to willpower as I like the whole Natural Origin thing, but somehow it feels like I'd be missing out without a damage aura.
Am I just being silly or is the aura a big thing for brutes?