I've been thinking, instead of heavy hard-hitting raidwides that kill when mitigation isn't on point, why don't they just give us a series of moderate raid damage hits during mechanics instead?
Let's take High Concept in P8S part 2 for example, instead of what they do now, what if, during the part where you have to combine 2 players to take towers, the boss marks one random tile with fire/ice and the remaining 6 players have something to do instead of standing there and staring at the boss until his wing starts glowing. Or maybe High Concept cast applies a minor bleed to everyone to keep healers on their toes?
There's other things they could do too, I think the problem of filler spam could be partially solved if most fights aren't just waiting for the next castbar.