GM trannies rarely leak.
The problamatic ones are the zf trannies which arent on teh 328 because of their plastic panels.
GM trannies have metal pan.
My at is rough as well. I think it's the nature of the tranny. Dealer involved hq and they ran diagnostics on my car. They checked for gear slippage and all was within spec. I guess I don't have enough damage to trigger an error.
I did a fluid flush to see if it helped..made it a little better but not 100% perfect.