I never see anyone using the melee mobs (guardian chain). They seem pretty pointless to me as well. Is there something we're all missing?
Most people around my might have at least one cannon tower which eats those guys up. I can see them being useful in lower might levels against people with poor defense setups, since you can just send them in to loot all the resources then leave without having to take down everything on the way. I don't think they are too horrible, its just griffins/centaurs are way more efficient.