Basically don't spam medica 2, and don't regen before the pull. After 1-2 transitions in Titan you'll need to shroud.
It happens to me as well. Doing Titan EM I WILL pull Titan if I don't watch threat. Based off cure 3 for stomps, and medica for tums, the threat shoots up.
Don't let people tell you what not to use. The tank needs to stay on their toes on AoE fights, and you have to know when to SoS