The Elder Scrolls III: Morrowind

Yes, Ur can be defeated without first taking out his Ash Vampire underlings.

Yes, as long as you have sunder and keening you can basically just walk by them.

Yeah, just tap that heart a few times with each and GG.

Yes and not only that you dont actually need sunder and keening to kill him, although it doesnt work correctly for completing the main quest. If you do enormous ammounts of damage to him in quick succession ex ebony dart of slaying from the bloodmoon expansion you can kill him without the scripted death

You can kill him without killing the ash vampires but i really recommend killing them because he killed me in 2 hits when i had killed all the vampires so he is probably extremly strong if you dont.

Yes and accourding to the un-offical elder scrolls website, killing the ash vampires doesn't actually hurt dagoth ur.

yes there is a way to do it without keening and sunder actually i don't even know where they are because i killed dagoth ur by using the original morrowind and doing the instant mastery of weapons cheat and then bought the GOTY and had my long blade past 20,0000 and marksman over 15,000 and there are the best arrows of the game in solsthiem at thrisk in a hollow tree stump which takes hunks off his health and then after he's dead just hack and slash away at the heart and your done. (OH AND BTW BEHIND THIRSK ARE WHERE THE ARROWS ARE some other cool little nifty things in there).