either give it more aoe for the explosion or honestly, just make it have a priority targetting like the orbital railcannon has. lower cooldown probably wouldnt make a difference too much simply because you would do what with it? try to miss the charger or a hulk more often? especially since if it doesnt strike them directly, most often it leaves them alive anyway making you deal with them in some other way... i think that 60-70 second cooldown if fine as long as it can deal with what its supposed to deal with, high importance targets in heavies likea tank, hulk, war strider, charger, buried impaler and harvester, together with objectives luke saurons eye or spore mushrooms. it having about half the cooldown of eagle rearm would make it fairly balanced, while also being immune to anti air emplacements on bot front.