I'll rephrase it. Next to the Daedra Lords, Vivec is the closest thing in the game to a god, other than Dagoth Ur, and
You don't need it to be nearly that high to hit most of the time, particularly not if you use splash damage enchanted arrows and point them at the ground under him.
EDIT:
I forgot what I wanted to point out through all of this. In Oblivion, the characters that comes the closest to having the kind of power Vivec or Dagoth Ur have are Mannimarco, and Mankar Camoran. Neither of them come remotely close to being remotely threatening. You can either cast the uberspell you have by then to instantly vaporize them, or wack them around for fifteen seconds as they ineffectually summon weak monsters and throw fireballs at you.
Not sure what you're trying to say comparing Vivec and Dagoth Ur to Oblivion's versions of the King of Worms and the son of the Camoran Userper. Both were, typical of Oblivion, horrible horrible abominations against the lore of the series, and game design in general.
In Daggerfall the King of Worms is this uber necromancer who becomes a god in the end depending on the ending you choose. In Oblivion he's some weakling Altmer necromancer with an ugly staff. Oh yeah, and as a nod, or rather kick in the balls, to anyone who knows anything about TES lore necromancy has suddenly been outlawed and all necromancers have turned into psychotic suicidal maniacs for no reason other than to provide a generic as humanly possible antagonist for the mage's guild missions.
In TES lore Mankar Camoran's parents were Bosmer. In Oblivion he's an Altmer...
Isn't it amazing how practically any discussion about TES naturally flows to how much Oblivion sucks? It's just, that there are so many reasons that it's impossible to list them all without talking about other stuff as well to remind you. It's like The Simpsons, except instead of saying "Hey, that reminds me of that episode of The Simpsons..." you say "Hey that reminds me of another thing wrong with Oblivion."