Firstly, sorry about the lack of an EGSNP this past Wednesday. A combination of lack of sleep and something unexpected coming up resulted in the delay.
There actually is a slow time spell in Fable 2. On its own, it's pretty good. Combined with high level offensive magic, it's broken.
It's a bit convoluted to explain how exactly the magic system works, but each spell has five levels of power. You can tap the spell casting button to cast a level one spell, but for levels two and up, you have to hold the button down for progressively longer times before letting it go.
You can mix which spells get cast at which charge, so you could set one spell to go off at a level three charge, and different ones at one, two, four, or five.
Point is, leading with a quickly cast Slow Time to give yourself time to charge up an area of effect offensive spell makes combat absurdly easy.
It also gets easier the more magic you have. Spell charging gets faster as you get more magic, so it's easy to very quickly use a level three Slow Time spell, and then charge up a level five area of effect Fire Ball.
I wouldn't say it's the most fun way to deal with enemies, but it'll get the job done.