Sure. Detect life so you know where people are, telekinesis to steal from across the room

Paralysis can be useful in a multitude of situations both in, and out, of combat.

It's some great assassin rp too: imagine being rendered immobile while your killer slowly approaches with a dagger, poison dripping off the blade... gives me the willies xD

No problem 

What about Detect Dead?

Well they could be, however thieves and assassin's usually involve stealth, and spells make both sound AND light, so they could give you up pretty quickly. You could get the perk Quiet Casting, but even then it still generates light.

Bump

Sure. I should've just said "the detect spells." But yes, detect dead will help if you're sneaking through a board with drauger

What about destruction spells, like runes or walls?

Any just general tips for creating a build that relies on heavy use of scrolls, some use of staves, and only limited use of actual magic?