I don’t think I’d risk a purple sun, not with I2. The other spells, though, are good. D&D, as you say, with a hellcannon is devastating.
Ashstorm and flames of azgorh are the two ‘mega’ spells that do all the damage (figuratively speaking) from the lore of hashut. Hatred is ok, but the others aren’t brilliant. But if you do cast ashstorm, you can watch ogres just melt away…ashstorm + destroyer = lots of dead ogres, ashstorm + magam cannon = lots of dead ogres.
my favorites are lore of hashut and lore of death.
my favorite thing to do in my RH list was to fly around on a lammasu with my sorc lord sniping characters with lore of death and then when Im set up drink the potion of speed and cast purple sun down a flank. combined with lore of shadow spam it was golden. but many people would call that crazy, and it was totally high risk high reward.