I have tried to come up with scenarios where it justifies its existence, but so far ... I got nothing. It is way too costly, does way too little damage, is static and so can't be redeployed.

...

I think I would use it again on a zombie map. I think it could be a good buff to help hold a city ... maybe ...

yeah I use them to kill hordes of advancing UGV (the other useless elite unit)

And I've seen that about as often as I've seen hordes of zombies in the regular maps.