yea, you're correct about 60 seconds.
For all its worth, if you're going to stuff yourself with potions and poisons, you can get a much greater return using combination of weakness of magic, fortify restoration, and fortify marksman and get much higher damage multiplier without needing to poison anyone. Since it will benefit from 3x from sneak attack. The rune will not.
Materials, I would not say is abundant, with fortify destruction you're looking at beehive husks, ectoplasm, glowing mushrooms, night shade, or wisp wrappings; I would only consider nightshade and glowing mushrooms relatively accessible. And glowing mushrooms show up mostly exclusively in caves, so you do kinda have to max out alchemy for the harvesting perk to have a constant supply.
If he wants more oomph, he's better off with fortify marksman, that can be enchanted permanently to his gear and potions. Cause all that prep just for a fire rune isn't going to do much to level scaled dungeon daurgr overlords everywhere.

And with so much prep skills his level is going to be high.