@totalrando I use all my tools at hand and have a lot of success in recovering bricked devices. The Oneplus3 that would not leave recovery after many, many attempts, I managed to sideload Android, which worked, then allowed me to unlock the bootloader, which makes it so much easier for future repair. I have sore fingers from the amount of power and volume button holding on these devices.
My advice is if a phone is bricked i.e. is totally dead, leave it on charge for 24 hours. If that doesn't work, charge it attached to a PC, not a laptop or plug in charger. I have got a lot of devices going again just by plugging it into a PC (making sure the PC is on) for an hour or so.
If it boots to the bootloader and that's all it does, try to erase/format the cache with fastboot. If that fails, good chance the storage (eMMC) has failed.
If you can get TWRP going, format the partitions and wipe the data. If it fails at that, it is either a partition table error or there is hardware failure. I have seen this lots on the Nexus4 and 5, repartition ZIP is fantastic here.
If all that fails and you always boot back to recovery, it usually means a hardware failure, CPU, eMMC, RAM. I persevere here just to make sure, and will strip the device down and look for any flaws on PCB's or connectors. Usually you will see moisture damage that can be repairable with some isopropyl alcohol. The biggest cause of shorts though is usually a damaged USB connector. Thankfully most these days are a separate cable as my solder skills are awful. That can cause all sorts of funny issues.
Once all back together, if it works great. If not I break it for parts.
So to me bricked is a dead phone, a phone that boots to the bootloader and stops, a phone that boots to recovery and stops or the phone that bootloops after you have tried everything....
