Dear ArenaNet,
Seeing as how there’s a distinct tendency for players to clump up into large blobs to take advantage of a multitude of AoE boons, this mechanic should vary things up.
I had a dream the other night where in a boss fight, the boss would occasionally reach out towards a cluster of players.
The hand then had its own, separate HP bar. If the players managed to get it down to 50% before it could land, the boss would pull it back in pain. If they could not, it would land, grabbing one or more player(s) and launching everyone else away from the impact.
Those grabbed would be helpless, like in the Jellyfish Fractal when the boss devours a player. They could try struggling to get free, but even if they do, there would still be the height to account for. They could instead struggle against being crushed, to avoid periodically losing HP while under the effect.
It would depend on the boss what it does then and I leave that up to people smarter then me.