I'm guessing this is one of two cases:
a) If the class can spec into melee (Shaman has Enhance, Druid has Feral/Guardian, etc) then IWT works... but if the class has no melee spec (Mage is a caster, whether Arcane, Frost or Fire), then IWT isn't working.
b) It is a bug, which will get fixed at some point, hopefully soon.

I'd really hope its a bug, and most likely it is.
The whole IWT/CTM was put in for players with disabilities, to make their play easier.
It was not put in for making boxing easier, even though it opened up melee classes to us.

In the meantime, Jewelcrafter characters can cheaply make this: http://www.wowhead.com/item=41367
That will turn your character to whatever the target is, at a range of about twice that of the furthest spells.