if the 20% goes through draenei will be a good choice for dk 4 ret, especially considering the team essentially despite being 5 dps is an endurance team at this point, staying a live while they oom is always a good thing.

i dont have firsthand experience, but from what i understand the ability to drop combat with shadowmeld with a druid so you can stealth is incredibly powerful, the question is how useful would it be for a multiboxer.

for the DK team its really about maxing your burst dps. i thought dps trinkets all shared a 30sec cooldown in which case you may not benefit greatly from being human, however, choosing a race like worgen for run speed or gnome for escape artist to keep you in melee range getting those necrotic strikes off might be more useful. the same might hold true for the ret team honestly. having an extra WoG cause you were able to close the gap while you had zealotry up would outweigh the benefit of the draenei heal.