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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The main reason I dislike this type is that they have a timer for zero reason. If you don't touch them they will finish before time runs out. If you hurt them they run and will finish before time runs out. Why bother with the timer if it never comes into play?