When you do it more than once, you will lose all mana if you didn't know. It doesn't give much flexibility at all. Without using a wand, a person can use bolt every once in awhile without having to use mana pot. rF Mana shield without high int/mana can still save you because it adds more "life" to the character. If a person ranks a bolt, it will add intelligence as well. It will help even more if person ranks Magic Mastery because they like whatever bolt they used.
There are other stuff a melee can carry on secondary besides a bow. Noone, but you, mentioned a bow. I am not sure what you have against my character, but I have said nothing about my character here. Also, it has nothing to do with this situation at all.
Sword/Blunt+Shield, dual daggers, and/or two handed type swords are other melee weapons that low level and high melee characters generally carry around. I rarely see anyone actually carry nothing on secondary. Many people (low or high) carry an ego as secondary, regardless of the levels of ego. You are clearly an exception if you carry absolutely nothing on secondary.
I haven nothing against your character, but I do think it's kind of dumb when you say "well they should just do ----" without taking into consideration their actual character limitations.
The phrase I was replying to was "used up a switch slot for a useless strategy."
What else would OP have on the switch slot? Does OP even have mana shield? How much Int and Mana does OP have?
I'm assuming, nothing useful, maybe not, and terribly low. In which case, CC Firebolt would cover the lack of range power (why I mentioned a bow, since he has no ranks in range and thus lacks such).
Also, carrying melee weapons on both slots is rather pointless, unless they're extremely different. For example, daggers and a slower speed weapon. However, again using the ranks to base this off, since OP only has Windmill ranked, it's unlikely that he uses daggers with low stun, or a shield resulting in low damage making Windmill spamming take longer. Without Smash, it's unlikely he uses a 2H sword too. He may have them, may have them equipped on secondary, but they're just as much of a wasted slot than a CC Firebolt wand, if not more.
For pure-melee players who haven't gone Hybrid, it's actually smart to carry nothing on secondary, since secondary weapons get screwed over my durability time decay.