I know we and others will still handle the trash with less damage. But i thought Ask Mr. Robot is all about optimizing my gear. And as a DD that means a much damage as possible 
And i and the others top DDs (in my guild) for sure don’t watch a video during trash because we want to be on top of the hill 
Last MC run i had about 600k on trash and 1,2 or 5% from that isn’t a really small number (nor a great, i know). But it is a difference.
Long story short, if i am the only one and/or the effort is too high i can live with that 
But some sort of option (e.g. a dropdown with hit i am going for) would be (very very very) nice. I need 0% thanks to skills, warlocks i think need 5% (for level 62 and below).
Kind of similar with my hunter alt. As troll with bow i need only 6% (instead of 9%) for bosses and i think 3% for everything below level 63.
Regards
PS A lot of “i think” because i’m no theorycrafter, thats why i use this side.