I dont see why people think volcano spells are out with Blizzard's one around. Theirs is rather..boring. Basically firebolts with arcs... Custom volcanoes tend to have:
1) eruption damage
2) lava and fire damage
3) the molten rocks that blizzard has
And ours tend to be fast paced rather than every 5 seconds. Really, their volcano might improve everyone elses' because they have custom models.