I can speak for Enhancement and most people's views on it from what I have seen: "I better hit big because I only get 3 hits then I get killed"... so they go harmonious or they try to make some funky Aurora deal that has no Crit.
But, when they have heals/not getting farmed harmonious/aurora gear under performs by quite a bit ... because fireflash gear just out paces it very quickly with haste and Crit (enhance just has tons of little incremental damage that thrives on crits and being able to get your CDs down).
It's easy to fall into the trap.
If I ever re-gear Slack, I'll probably trade up 20% mastery for more crit/haste... because the games where you are not just farmed by S tier... fireflash just does more overall and you get the extra burst potential. Having all of your gear with slots and at least +2 agility per slot is enough raw damage on all abilities... just do them faster and have them burst is the key.
There are a few gear choices where I can flat out say "you are wrong" when it comes to enhance and the "fireflash choice"... you are wrong if you don't take the goggles and add 32 points of crit... and you are wrong if you also don't run the dragonling with +20 haste +10 mastery/verse. That is a good indicator of "fireflash power".