his winrate is so low because people are playing him like old GP and dont know how or want to bother with learning how to use barrels.
ive been playing him almost exclusively since the rework and his barrels is what you HAVE to learn how to use.
here is a tip, put one barrel down out of range of your opponent. this will create a zone where enemies wont want to go near you in fear of getting hit by it. once the barrel is 1 hit put a second barrel down to chain with the first ahd IMMEDIATELY detonate the first barrel with Q. if done right your enemy wont be able to react fast enough and all he can do is focus on avoiding barrels. in lane this creates some of the best zoning in the game, especially against other melees as they cant do ANYTHING about it except avoid the second barrel placement. the point of his barrels is not to place and immediately shoot. you have to be clever with chaining them together. thats why you get 5 of them with short recharge times.
its more tricky in teamfights, but the result remains exactly the same. Best of all is that most of the time the enemies will be to focused on the actual team fight rather than trying to avoid or kill your barrels. i remember chunking a nid for 90% of her HP with one barrel and used ult to finish her off. i use to think that his barrels were VERY limiting, but i couldnt have been more wrong. infact id go as far as to say that when people start learning him it will be nerfed. the wave clear is just insane.
anyway im talking to much, i dont want him nerfed.