Re: this is bad! WHATS GOING ON?
Overhauling disc brakes can sometimes involve more than just replacing pads. Apart from sizing and skimmimg the rotors to ensure the new pads bed in correctly, other things should be checked to ensure that there is no binding. The pistons should move smoothly in and out of the cylinders (albeit with quite some resistance, which is normal), and the caliper assembly as a whole should move side to side to allow for takeup with pad wear. Some assemblies are quite tight but move they will, and must.
If the caliper assembly is frozen (which is common enough) it cannot move laterally and typically one pad (the inner) will wear down to almost nothing whilst the outer pad will look almost new. Overhauling brakes means checking all these things.