pink wards last the whole game, and if you know he's going to camp it anyway, kill him
The problem is that he can literally take it as soon as it spawns and take zero damage from it. When I say zero, I don't mean he's not taking a lot of damage while doing it, I mean he's literally taking NO damage at all.
When he can take it this early you have to dedicate resources to stopping him that could be used in other places, such as CSing and gaining EXP, while his team doesn't. This gives them a huge lead no matter what path you choose, since dragon doesn't give gold anymore so even if you beat him to it you'll fall behind on CS and EXP.
Also the 8% damage boost for his team before they even take their first RTB is insane.