Good, welcome to the arena, where the fun begins
Before everything what i did with your AI was just an over exaggerated version of it to make my point about cutting things (and a good example of what not to do to retreat! ) and separate scoring and catching is probably a bad idea anyway.
About yours, its good over all, a very good start i think plus a lots of good things you can start to work on.
Oh and yes you don't like your shotgun yet, of course it's the most complicated bot class (i think).
But he is the only one to do what he do. and he can do a lot. so learn to cherish him and he'll soon become your MVP.
Now some though for your AI.
Shotgun is a coward he needs to flee more, two enemy targetting him, bam! you run, but come back quick to disrupt them again.
Don't try to make him engage combat at medium range too often he is good at short range but if you put him too much in danger he dies in a blink.
Machine gun his tanky as hell, so not bad at caring resources at some point in the game (close to a resource and to an ally base, don't drop your resource too quick cause he gonna score anyway) and don't need to make him flee too much (like you already started to do).
He's so slow at aiming that you should consider focus fire on the enemy he is attacking at long range (if sheild his low even if fleeing this move will grind a bit of it's live bar and it can break and hold assault bot from pushing yours)
Sniper should stay and engage fight at long range and should also try to bring support to his friends in needs. (it's the bot class that a know less about for now so I don't have a lot of relevant things to say about him).
and for Assault well you already knows what to do