Tank supports

Braum got his damage on his Q lowered. Tahm got his post 6 damage lowered for max health scaleing at a time in the game where no one has much max health and he didnt even need help. Neither were problem champions at the time. So if each champion has an allocated power budget and these two were nerfed when they weren't even problems why wasn't another part of their kits buffed to compensate. Stronger or longer slows etc. ?