Collective Unconscious is the strongest AoE heal in the game (200 potency, 6 ticks for 1200 potency), and it's free to boot, it doesn't seem so outrageous that it's also the hardest AoE heal to use. The fact that it has a smaller radius than other bubbles, and much smaller than AoE heals, roots you, and prevents you from casting, are collectively very strict limitations that bring a powerful, situational heal down to a niche ability. I feel like changing or eliminating any one of those limitations would bring up CU's game and make it more usable. It's Nocturnal Sect effect, though, is nowhere near as powerful, and needs a lot of love to become more usable.