Position 1: Trash doesn't matter! Only boss dps/kills matter!
Position 2: Boss kills = progression. Time spent on trash = less time on progression.
Needless to say, while I hear position 1 frequently, I'm in the position 2 camp.
I'm not recommending gearing/glyphing/spec for aoe/trash (unless you want to use your second spec for it), but I get sick of people losing focus and/or not bringing their 'A' game to trash. My raid has wiped three times in the past two weeks on trash, which is really inexcusable, and a huge waste of time. Wiping aside, killing trash quickly and efficiently has significant benefits for the raid.
So, to that end, I'd like to remind all of us to maintain focus and not be semi-afk during trash. Do your best! And use your cooldowns. That DRW/gargoyle/ghoul will be up when you pull the boss, don't worry. Pull out the stops and perform your very best, during trash AND boss fights alike!
