Those guys didn't even really stuff Brock's takedowns. Brock only shot one takedown on Overeem, and it was a half-assed single leg. Brock was known for his powerful double legs. Brock landed one takedown on Carwin in the second round, and he took Cain down right at the start of their fight. Overeem is literally the only opponent he didn't take down, and you could argue he barely even tried for the takedown.
Fedor doesn't exactly have great takedown defense, and just a couple of fights ago got taken down by Chael Sonnen, who despite having fantastic takedowns, is a middleweight. Sure, Fedor is way past prime, but I doubt Brock would have any trouble putting Fedor on his back. Could Fedor get back up? That's the question. Maybe he could even get the sub. But I think it's guaranteed that Brock would take Fedor down pretty quickly.