I’m glad you got it, but I regret to inform you that it has only ever been one chance per week, regardless of how many alts you run on. I believe it drops to a 0% chance after the first kill of the week.
I would have spent 150k if I could have avoided farming that stupid raid for so long. 
OOF
If we are talking actual sets, then the season 11 cata gladiator gear for pallies. I don’t know about underrated, but I don’t see it used often enough for my taste.
But, I almost always prefer wearing simpler outfits for transmog. And, I really enjoy my biker/punk/enforcer mogs that I’ve been doing for 2-3 years; they are simple, but I love them.
Here’s one of many characters that are wearing one of my biker sets, which vary by armor type and sometimes RP flavor.
I’m going to drop some images of some others here, but to preserve vertical space I’ll put them in a details block.
And another clothy, this time forsaken, that’s currently deleted.
Also, 
to @Beefdaddy-Argent-Dawn, since seeing his on reddit made me really fall in love with this type of mog.
You want a burger king crown?
Look at the 10.2 paladin set for normal.
This my favorite transmog.
I hate they never released the green one that was datamined before they came out
Kul tiras dungeons. Mythic recolour. The other colours are cool enough as well, but they’ve got nothing on the red imo.
Me too, dude!
This sha set is pretty cool but I never see anyone with it on.
I never see the firelands priest tier (any of the recolors) be used, that set is actually super neat.
sadly its a dress…
Look like the Green Lantern.
Castle Nath Mail set
HFC Monk set
Mythic Sepulcher DK set
The cata pally set is gorgeous. I only regret i was maining my priest at the time and didn’t get the elite red color for pally.
I refuse to wear it because it just reminds me that i don’t have the elite variant
Not any full set in particular, but many of the unranked hunter sets pre-WoD are pretty good looking. In fact I think I see people wearing the Wrath pvp sets the least, and they’re both cheap and (generally) well designed. The classless raid sets from Wrath, too.
Anything where you can hide the armor… Sometimes the answer is it all sucks
Of all the Tier 3 recolors/remakes, I thought Paladin was the most faithful. I think this is a very underrated set and rarely see anyone wear the 25 or the 10 colorations.
