Ice Splitter Uses Over Octopus

Well you're not really answering my main question. Why would getting Ice Splitter first make gaining levels faster?

My issue is ... what am I freezing exactly? With the areas to train for 70/80 in the guide, I think I would be better off just using Invis Shot or Burst instead of freezing. And if i'm using those sort of offensive killing skills, wouldn't Octopus be better?

Also getting the most out of your octopus would also require strategy as you gotta know when to drop it! ;-)