Dead phone. replaced dock. still dead. Battery?

This is a belated answer so hopefully it can be of use to folks who search for and find this question.

I would say that when troubleshooting charging issues, I would do the following (in order):

1. Change the battery. The battery s the weakest link in the entire phone and certainly for charger related issues. It is also the easiest thing to replace. Use a battery utility, such as coconutBattery (for Mac) or 3uTools (for Windows) to test the battery prior to removal. Anything less than 70% of design capacity will require replacement.
2. If the battery is in good condition, you can use a USB Ammeter to determine if the phone is really drawing current when it says it's charging. If it isn't drawing current, then I would change the Lightning/Charge Port.
3. If a new battery and charge port still don't resolve the issue, then you either have faulty replacement parts (possible) or a logic board issue.