Let it Burn, as a signature spell should be both insta cast (could easily link it to increments of frozen solid like E'Ci's) and hit for close to the tooltip (it never hits for more than 40% of the tooltip maximum due to many contributing factors, the main one being spell damage is severely mitigated compared with direct damage of other classes). But given there is nothing for a Wizard like casting while moving (without spending aa points to do it, then it's a measly 18 seconds) and having such a long build up time for increments and resetting Rays of Disintegration from slow casting Ball of Fire, LiB enhancement would be a valuable addition to the wizard casting order IF it was insta cast and maximum hitting at all times.