Why encounters with a difficulty slope are bad

[Ashkendor]

I dislike enrage timers though, putting a hard limit on a boss is stupid.

I prefer soft enrages, myself. With a soft enrage, you can sometimes juuuuuust squeak in a victory, the healers struggling to keep people standing and everyone pouring everything they can onto the boss in a last desperate burst. It feels so good when you win like that! With a hard enrage though, the boss just says: lol no and wipes your entire party with one fell swoop. It's boring. :|