Legion Emblems, focus on bosses or rares?

Hi,

I don't have a ton of movement speed and using Frost Blink so i am definitely not killing as much as I could in the Emblems, so I was wondering is it more important to kill the bosses when they respawn or just focus on the rares and force the respawns as fast as possible? Really no idea on how the loot distribution works for these.

I only have 1 timeless, so i will probably be doing normal emblems if that makes any difference. I tried a timeless with a buddy and the bosses didnt even lose health against me in the last minute or so, so probably out of my capabilities atm.

Thanks,