I find most mission finales pretty boring. A few waves, mostly scripted, a few elites/specials and a gimmicky event/mini-game which feels like a boring chore to advance the whole thing.
The Boss endings are even worse because they are often less threatening than random bosses and rely on elites/minions spawning right behind you in a tight arena to do anything. Is Halescourge harder? Yeah, he has everything cheap the stormer/leech have + fat unblockable DOT attacks.
I think the ending should be the most memorable and epic moment of the mission, the climax, but they are not.
As personal example:
Against the Grain the map starts building up great in the first house and peaks at the barn boss. Then it goes straight downhill with a few hordes but mostly a small stream of weak enemies and some fixed spawns. Predictable. Repeatable. Boring.
Righteous Stand starts great at the first tome w/ possible boss then has a good arena (which is better than any boss arena) and goes with a good pace up until the very end. Then it’s a poorly illuminated church (which makes no sense and adds zero dramatic effect) where you have to make a suicidal effort to have a chance to wipe (I’ve never wiped there, ever). With great luck you can get sniped by a ratling hidden behind a window or a globadier.
My favorite ending is The Screaming Bell. A brief mini-game, no chore, a few waves + boss and you still get a threatening amount of enemies in the final stretch before the portal.
Hunger in the Dark is ok. A single Bile Troll. No waste of time.
Athel Yenlui would be next. It’s fully scripted waves and could do with something actually threatening, like a real boss (even an ogre), but it’s ok.
Worst ending is Fort Brachsenbrucke. A mini-game with so little interaction that it feels like a cinematic and the “threat” is a handful of slave rats that can’t even be considered a wave. When it feels it’s done you are also forced to do the stupidest fetch job. You have to go ALL the way to the other side of the arena for nothing and in the process about a dozen or so vermin will be injured. Just enough that you will be made to slow a little and risk dying of boredom.