I have tried this ally a couple of times. He is not as bad as he seems. If you are able to reach 4 , then you will not have any problems with enemies and you can one shot many smaller minions (in single mode). Ranged keyword is nice bonus, which can be used to vanquish some flying bats.
He is quite expensive and that is the reason why we do not see him so often. But one copy for some specific scenarios could be good choice.