Just like in Well of Radiance. Bubble is made near totally worthless when you can easily get frozen and melee killed instantly. Just make it so that when you have the "Armor of Light" buff (only available when inside of a bubble), you can't be slowed or frozen. You already can't shoot out of it, so at least make it somewhat more of a defensive super.
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I’ve went as much as saying opponents should also be automatically suppressed when they’re in the bubble. So they’re not able to pop super inside of it. Because if it’s just one guy in a bubble, a tether can easily be popped inside, or a blade barrage even.