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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They run way too fast and too soon. You literally need a sparrow to keep up. You have to stagger lock which is just bs.