If you have reliable countdowns on your pulls, on the appropriate encounter, it's totally worth it - EVEN IF you do it 5 seconds before the pull - but that's a bit extreme. You could do it 3-4 seconds before pull and have it all done in 1.5 seconds using a macro like this:
/script LearnTalent(13)
/cast Guardian of Ancient Kings
/equip Helmet of Radiant Glory
/equip Battleplate of Radiant Glory
/equip Gauntlets of Radiant Glory
/equip Legplates of Radiant Glory
/use Golemblood Potion