It also depends who you plan on fighting. For instance, as Arkellin, Vortex was incredibly useful. Fighting Outlanders, they're all basically flying, and you could usually delay defenders by simply putting a Vortex right under the huntress. Pillar of lightinng also does insane damage against outer defenders if you're outdoors...like kill them in six or seven of them. Also, shield of electricity is great against opponents who forget to switch to non-metal weapons, or who don't have them. So, like I said, depends on the types of foes you're facing.

Against Battle, I'd drop air first, maybe fire (though immolation can be nice), then water.
Against Outlander, I'd drop ooze first, then water, then fire.
Against Fortress, I'd drop fire first, then water, then ooze.