Having the raid move to opposite side of the platform from where the spirits spawn, as well as putting a frost trap down underneath the spirits, and PREFERABLY another one on their way towards the raid to make sure they stay slowed, helps out a lot as well. You should be near the raid, with the MT on LK right behind you, with the raid right behind him, ideally. That way when the spirits get within range of you, they should all be on the ground, and thus within easy range
ABC----------------CBA. Where A is the raid, B is the MT, and C is you, if that helps draw it out anymore. Just run into the spirits as they get close to the raid, and they should blow up without you needing to get aggro on them. If a couple split past you, that's when you want to use your taunt/aoe taunt (as long as it doesnt grab the LK... warn the MT before you do it just in case, so he can taunt back)