Discs rubbing no matter what I do So a couple of days ago I regreased my back wheel hub bearings, put it back together so there's no play, golden. But when I put it back in the bike one side is constantly rubbing. 

Tried loosening and tightening the caliper clamp bolts, no luck. Checked if the rotor is bent, it's not bent. On a closer look of the caliper without the pads in I noticed that one of the pistons is sticky. So I cleaned the pistons with alcohol and put some mineral oil on the sides and pumped it and pushed it back in a few times until they come out evenly, still rubs. Bled the brake, still rubs. Adjusted my hub over to the side it was rubbing, still rubs.

I have literally done everything except change the pads, but I doubt that's going to work either. What is going on? It was fine before I cleaned out the hub, apart from the fact that it was gritty when I rode it, which is why I cleaned it.
The first thing I'd check is that the wheel is mounted in the frame straight and fully in the dropouts - sounds stupid I know but we've all been caught out by things like this.

I wonder if somehow your hub is not running true, either because it's not running true on the axle, 

Remove the brake caliper, spin the wheel with the bike off the ground and verify that the hub body does not have any run-out. Do the same with the disc rotor - you can attach a  trimmed zip-tie to the seat stay to give you a point of reference. I'd check both lateral and radial run-out.

Once you have verified the rotor is indeed true, re-retract the pistons and align the caliper carefully. USing a flashlight and a piece of white paper to look down through the caliper can help you spot where the rubbing is occuring.