If you think you are over correcting then set the sensitivity lower, you will snap turn a lot slower but it will help with aim. I'd say the biggest thing in D2 PVP is recognizing your weapons strengths, the distance between you and your opponents, and how many there are. When to go aggressive and challenge (1v1, you are strong he is weak) and when to fallback (1 v 2+, you are weak and he is not, etc). If MIDA is your primary its strength are mid range, at close range you should probably switch to a SMG or sidearm secondary instead of trying to finish off with MIDA. You have to learn all the PVP maps and figure out the shortcuts, what halls are good for CQC and what are good for long range snipe/scout, etc.
It does take quite a bit of practice to learn how to work with the aim assist instead of fighting it, you can just practice with PVE though - go to Titan and do the lost sector on the Rig, you can follow the video here to get to it
There are a ton of mobs all clumped up and it fucks with auto aim a lot, so its a good place to practice with your favorite weapons so you get used to the magnetic pull a bit more, good for practicing with sensitivity and fast turns too. This video is a bit old but I watched it a while back for tips when I first switched to sticks in D1. I also use a control freek height adjustor like this guy, find it better for accuracy. Buy em at gamestop for $10.
The guys tips of watching your gameplay recordings is also a good idea to see how you move and aim.
