I'm sure as hell that I don't want to deal with conflagrations during twisters and divebombs during heavensfall. Anyway, I personally think that the encounters are pretty well-designed. The final boss of each coil were intentionally designed that way to test how well each player can adapt to the ever-changing battle till the enemy falls.

Though, it would be nice if you could have provided some of your own ideas into the mix and elaborated your reasoning why the encounters you've listed are 'good' or 'bad'. I can't read your mind. I don't think you've made clear on what makes a good fight.