I started with:
HTC One dual sim 802w (Chinese Unicom); running stock Chinese Jelly Bean 4.2.2.
Chinese 4.2.2 bootloader unlock, CWM recovery, root, S-off through WWE European 4.4.2 if you're interested:
My initial task upon arrival NIB with Chinese Jelly Bean 4.2.2 was to remove chinese bloatware, install CWM recovery, and root following Marrk Daviid's instructions.
Pounded my head on the wall repeatedly trying to get my Windows 8.1 computer with USB 3.0 to work using assorted usb drivers, installing and removing HTC software and multiple HTC drivers without getting a connection for fastboot or adb to get my id token.
I found tobesedated's thread Guide - Suggestion For S-off On 1.55 HBoot Using Ubuntu , then followed pt's blog posting How to fix the adb no permissions error on Ubuntu Lucid to set the udev/rules.d/51-android.rules file to get adb to work, and I was able to get the bootloader unlocked, run rumrunner S-off, CWM recovery and rooted.
Converting to WWE European ROM 4.2.2 then 4.4.2:
I decided to go European so I could update to a Western KitKat, and used fastboot to flash the WWE ROM from shwetkprabhat's thread Guide--HTC Dual Sim 802w (China Unicom), apply WWE European RUU, OTA & CWM or TWRP ( PN07IMG_M7C_DUG_JB_50_S1_HTC_Europe_2.19.401.1_Rad io_1237.21.28.0627_release_326125.zip ) using my old Linux 12.04 (Precise) machine after clearing cache. It installed the stock bootloader also, and I didn't mod or change anything, until I received the two small OTAs and a few hours later, the “big” OTA automatically and OK'd the install for dual sim 4.4.2, and waited until the update completed, and root was GONE.
I then had: WWE international 4.4.2, an unlocked bootloader. S-off, NO root, NO custom recovery,
I (re)installed the modified custom recovery for dual sim (called 802w.img) extracted from HTC_802w_CWM_recovery_188.8.131.52.7z posted with Marrk Daviid's instructions and then installed UPDATE-SuperSU-v194.zip from Chainfire (placed in internal storage) through recovery.
After selecting reboot I selected NO for both options (the defaults) and upon restart I had root. If I repeated the process selecting the fix root option (first question No; second question Yes-Fix root) I lost root. I reinstalled above SuperSU through recovery, answered No to both questions and root was back (Root Checker Pro) and functional (and no tampered flag either).
Do I know why/how it worked? Not a clue, but it did work for me.
This fool has now blindly run where angels fear to tread, I hope this information is helpful to the gurus and cautionary to the brave/foolhardy until confirmed.