I recently did an all hybrid playthrough where most of my spells were used at, or below, the INT requirement and I found a lot of the environmental affects were still very useful. Even if the direct damage from flare wasn't great using combos to create coke points and block LoS was essential time and time again.
Like you mentioned there's several debuffs that ignore saving throws, for example rain and bitter cold is a fantastic way to freeze almost anything.
