I would not say they are useless. It is a very cheap upgrade and when the first CC is over, it might very well be less then maximum range to the next. The mutant unit might then also have lost quite a efw models and them flamers could be just what you'll need to even out the odds.
And of course TheCage is right, there are some spell you can use but since these are minor ones I did not think of them as they are in most cases useless.