Mouse Instability (Gameplay)

So this has been going on since around the time of the last patch, Happens every game since then. Frequent "sluggishness" of the cursor, seems to drag/lag around instead of just going where it needs to go, happens more so near the mini map area of the screen but, the cursor also just does it randomly at times of play, which make it very difficult to last hit, kite, or even just move around.

Many times of trying to last hit/poke/attack, my champion will just walk toward the location instead of attacking the target. It also happens when trying to move place to place by using the mini map or even clicking normally around the screen, I've experienced my champion walking to a new location or just stopping all together which both result in death half the time.

The frustration of trying to play any game mode at all with this happening non stop is pretty ridiculous.

Before I hear any comments on how its most likely the mouse, or something with my computer, or telling me to defrag and restart. I've done all this many times, checked online for different methods on how to fix this problem, even went out last night and bought a new mouse thinking my old one was just some pile that needed to be ran over with a car. Sadly after all this it continues to happen and since it only started happening recently (last patch kinda recent) I'd have to assume its the client itself, I am at this moment currently installing League Of Legends again, after uninstalling it, defragging and restarting my computer.

Some helpful advice/fix on the situation would be great, Thanks.

Ps. I've also had friends I play time to time with on here from around the U.S tell me they also have problems with the cursor and "sluggishness" of the mouse when trying to do pretty much anything.