Really easy to beat. The overseer will spawn and they go fast but once in position the come out of ball form and walk. They walk so slowly and will only attack when close enough. If you do the old fashion walk backwards with a pistol (or any gun) and shoot it is a 100% kill without damage. They drop element and you have to pick it up so tek users can tek power there way through it.
These things will destroy any and all structures you put in front of them. They can and will destroy metal as well as tek. Nothing is safe from these things. If you are on Genesis lunar biome these things are everywhere along with the flying ones. Be careful out there guys.