I keep consecrate up and use holy wrath when they've all spawned and focus on killing the black knight asap. That way they'll all explode at the same time, near the paladin. Sometimes (although rarely) one or two will reach my group (which is spread out and backed up against wall), but a well timed chain heal (timed to hit after explode) will fix it. I follow up with heroism for phase three (and use cleansing + resist totems and shadow resist aura during the fight). Frost and shadow resist is really handy for phase three, which can be annoying without a dedicated healer..