Abathur is great, but like many heroes, he takes a while to really come online, and until he does, you're going to be at a big disadvantage while laning and fighting. Your team needs to internalize that they'll be fighting 4v5 essentially, but a lot of people still play and lane as if it's 5v5 which leads to over-extensions and non-defensive play (getting picked off is so much worse). That leads to giving up lots of unnecessary kills which wipes out the incremental exp lead Abathur builds, which kind of negates the whole point of Abathur. I love playing him and Murky though because of how impactful they can be mid-late game.
So in lower level games where misplays/bad strategic decisions are more common, he's often a liability. It's just easier to win if you had been playing someone else. But as the skill level rises, I think he really starts to shine.
