ck,
You want to keep the slider pins and the tubes the bottom bolts slide through greased. From what I've seen it's not unusual to suffer uneven wear with this "floating" design even though it's supposed to cure it.
It sounds like possibly the metal backing plates may be missing if the piston shape is manifesting itself in the front side of the pad. My first problem was a stuck caliper caused by degraded rubber piston boots, locking the piston, preventing it from pulling back. This is easily spotted when the caliper is swung back off the pad mounting.
Glenn