I've done a few of these events, and generally (if they're champion) you need a least 4 people to even ensure their shields aren't constantly recharging. Even if you have a lot of people, he just makes a beeline for the exit once you start hurting him. So far the only one I've completed is one where we had multiple titans constantly punching him on and off. which I'm not sure this is the intended way to win.
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Using AoE grenades can cause the boss to stop moving in the direction of their goal. That's what I used for one on Earth. The easiest one I've come across is the servitor on the Moon near the entrance to the Temple of Crota area. The servitor doesn't have any shields which is nice, just a crazy amount of health.