Hussar said:
You accuse me of not reading the modules recently. That I'll cop to no problem. And, it's quite possible that maybe it's my memories that are cloudy. But, then you accuse me of not listening. Well, I did listen. I just happen to not agree. When all of the major NPC's CANNOT be killed before a specific time, that's a pretty bloody LARGE plot railroad. That means that the story is more important than the decisions that the players make.
Verminaard appears in DL2. The heroes are tasked with undoing/preventing/interrupting his plans, and this is a challenge they're easily up to doing. In the books, this is even where he dies - he's killed at Pax Tharkas (although like many cinematic villains, you never see his body). In DL3, Verminaard doesn't have much to do with the PCs other than annoy them and keep Elistan busy, so he's of little consequence. In DL4, the heroes finally get to face off with him and his cronies and kill him off.
Compare this to the changeling NPC who keeps showing up in the Eberron modules. He's a fake vampire or something, but he's a recurring villain. He's Eberron's Verminaard, essentially. The heroes have other things to do - they're not ready to kill him off, so he's a recurring character until they do.
Berem and Fizban aren't bad guys or villains. Neither is actually essential to the series other than as potential climactic characters. In fact, it's possible Fizban isn't Paladine, just a crazy wizard. It's also possible Berem is just a red herring as well. They're recurring NPCs who lend some degree of continuity to the story but they're not exactly targets for the PC's wrath.
There are some other recurring villains - notably, the Dragon Highlords, but then apart from Kitiara they don't have terribly much to do with the PCs other than loom on the horizon. There are always other NPCs and villains to worry about, challenges to overcome, and evil plots to derail. The heroes get to take out bad guys fairly often - they get rid of Feal-Thas in DL6, various opponents and ogres and bad guys in DL7, a number of NPC lieutenants and generals and spooks in DL8, and in DL9 they get to infilitrate Sanction and take out all kinds of major NPCs such as Dracart and Wyrrlish.
In DL10, they get rid of Cyan Bloodbane (or at least stop his nightmare). In DL12, they foil a number of villains from Balifor all the way to sunken Istar. In DL13, there's admittedly not a lot of major NPCs to fight, but there are plenty of other things to do (and the ending of the adventure to determine). And in DL14, all bets are off.
Honestly, the mere fact that the adventures were designed around the idea of the heroes doing things other than just fighting the boss monster at the end of the dungeon (which they do in DL1 to kick things off) was pretty radical. Each module becomes episodic, has specific challenges, and multiple routes or means of achieving those (especially after DL4 is done with). Like Shackled City or other modern adventure series, there's a plot that governs a lot of the events and background, but it doesn't shoehorn the heroes any more than you'd expect it to.
Trust me, when these things get rewritten and revised, a lot will be changed in order to make things more customizable and adaptable to the needs of an individual group of players, but the structure will likely remain focused on the epic story with the player characters as the central actors. To change that would make no sense whatsoever.
Cheers,
Cam