I will leave my seal on you!
Sub does want to play defensive, he is mainly a defensive character that can be played offensively, so you do wanna get him close to catch him with the Klone. It's all about stop aggressive play, like I said earlier. You do have a good point regarding the Birdarang though.i do think a good robin is a tough mu but remember that throw clone does a lot of dmg for very little resources. (132 on robin). they cannot eat many of these and i've found success in certain spaces in neutral with clone out and f3 pressure. when robins get over confident with birdarang, if clone is out and the spacing is right it's very easy to throw clone and hit him on reaction. i actually try to play in a range specifically to do this and i use a lot of meter on mb f3. it creates a weird space for robin where he becomes scared to use projectiles because he eats clone throws even from relatively far away, but he is hesitant to engage because of threat of mb f3 or sweep when he does. he's like scarecrow to me in that at first i thought theres every reason he would dominate the neutral vs sub but in reality it doesn't really need to play out that way if you are careful with spacing.
where the mu gets hard imo is when robins start to get a pressure train going. that's when the relevance of his normals through clone and his range in general becomes an issue because you are forced to play defensive, which isn't what sub wants to do.