..never really used Power, Lucky Day, Precision, Speed or Meditation - the spells that are bundled into Day of the Gods.
I dislike you have to be master to cast them on the whole team - if expert was enough, as it is the case with the spells that Hour of Power consists of, then it would be another story.
Lots of spells from the mirrored path are either useless when you get them or too expensive to ever be used - I do however like Prismatic Light (used it against Snergle's army once - what a joy), Dragon Breath (to wipe out warlocks and grand druids from a distance) and Shrapmetal (against Cuisinarts in close quaters).
Sunray can't really match Meteor Shower or Starburst, but Moonray is a nice area spell for the outside if you can live with night fights.
I have though used Mass Distortion to a fair amount inside the Cave of the Dragon Riders - love to do 400+ damage to the Wyrms.
Dark Containment is a joke - it really works best on peasants when bored.