I have to really take issue with this too.
I'm puzzled as to what you mean when you say "too". If anything, I feel that Kovacius reinforces some of my opinion. Ultimately, Dagoth Ur struggles to match the build up he and the Sixth House are given. All the lore, no matter how interesting, is devalued when it fails to shine through when he come face to face with the real thing. It's hard to reconcile the all the lore trying to make the Sixth House seem deep with the fact that in the present game they're bathing in all the trappings of generic evil; insane babbling, hideous monsters, evil lair, grostesque rituals, and more. Sure, Dagoth Ur might show a bit of honour, but what a shame hardly anything was done to build up from that. In context of the rest of the Sixth House in game however, the whole honour thing is only slightly better than when a villain foolishly tells his plan to the hero or gives him a "last request" when he thinks he's got the hero beat.
The appearances outside of the final fight do not make him unique or any less cliched.
No, but what it does do is give Alduin more of a presence in the game, which is the main thing I take issue with between these two. Let me call upon three other examples from Morrowind. Venim, Dren, and Gothren, who could be considered the villains of the Hortator quests, in my opinion do a lot more to hinder the main character than Dagoth Ur. What's great about these three is that rather than resorting to sitting in some tower while sending lowly minions at you, they step out and do the job themselves (most noticable in the case of Venim). These three were a lot more proactive than Dagoth Ur in their efforts to stop you, and I wish they had gotten to play a bigger part in the story since I really liked them.
Similarly, Alduin is more proactive than Dagoth. He's a busy dragon in the story, and we even get to see it. Skyrim MQ spoilers ahead:
Spoiler This is nicely demonstrated when the Dragonborn learns Dragon Rend, at which point Alduin shows up in the flesh in an effort to stop you, unlike Dagoth Ur, who seems content to wait in his tower will you aquire as much power as you want after getting Wraithguard. Perhaps not the smartest move on Alduin's part, but one I didn't see coming when I first went through the main quest, and one that even for a moment gives him more personality than an insane, arrogant immortal in a tower (as Alduin seemed to have a moment of panic). Surely, Dagoth would have been smart to send out his strongest minions to attack you in your sleep and take Wraithguard. All we get from him are weak Ash Zombies.
Of course, which is better is highly subjective. I'm just not too fond of the dark lord who sits in his tower all day, no matter how fasinating he might be.