Why would you nerf a character sooo much

Why keep nerfing characters to the point they arent usable in the advanced story line not all of us play pvp believe it or not some of us used to enjoy story mode until you nerfed that away from us. All you people complaining about how strong a character is in the pvp modes dont click when you complain gearbox instinctively weaken them they did the same with BL! and Bl2 they dont care a bout balance they just try to please everyone who complains this then makes the story unenjoyable and unplayable