So after struggling for days a with battery problem (my country just doesn't seem to have a HTC Sensation XE battery, and I didn't wanna degrade to a Sensation's), I got the idea that since my battery has gone days without any charging, it might, just might, be able to hold some charge again. So I put it back on charger, and voila, it was able to charge. I tried going to fastboot, but my PC couldn't identify the device (FASTBOOT warned me of a very low battery level), but in the end it didn't even matter (Love LP).
Initially, android was able to boot on battery, but it didn't recognize the AC charging, and the phone shut down immediately after pulling out the charger. After multiple tries, it finally recognized the charger, and I am afraid to touch it lest it dumps me again.
Apparently, it also solved my touchscreen issues (I didn't have to reflash the firmware). Taking a guess, I would say that the low voltage level cannot allow the touchscreen to operate at all (the POWER and VOLUME buttons worked fine). After my phone recognized the charger though, the touchscreen came to life as well.
I am posting this so that anybody who runs into similar issues can benefit.
What didn't help me:
- A similar HTC battery (for Desire I believe) with 3.8 V rating (Sensation XE has a 3.7 ~1700 mAh battery).
- The HTC Service Center. The guy told me that the battery is dead. Fair enough. Apart from that though he put the above mentioned Desire battery and when the touchscreen didn't respond he told me told me that it would cost Rs 8000 (~$126) to replace he whole screen). So better watch out at the HTC Service Center (at least in India, I am very disappointed with their service).
Jam that THANKS button. It only takes one finger.
Device: HTC SENSATION XE Beats Audio Z715e
Android Version: 4.1.2 | Kernel: 3.4.10-SebastianFM-1.0.3
Firmware: 3.33.401.106 | Radio: 11.76C.3504.00P_11.29A.3504.18_M
HBoot: 1.29.0000 (locked, with S-OFF) | Recovery: 4ext Recovery Touch 22.214.171.124 RC9
SD Card: SanDisk Ultra 64GB microSDXC Class 10 UHS-1