would whoop you in a straight up melee fight at low ranks.
If you are fighting low hp classes with poor defenses (ie: mage. You can expect them to flee out of combat on a whim and run/quaff/teleport if you icicle them, for example on the eastern road. If you catch them resting after a ranking round, partially injured or in combat the element or surprise should do the work for you.
And really.. there are wands that cast the majority of lower rank invoker spells (including icicle) so even shifters should have option open to them, even if they get a crap form or aren't off major.