Here is an Android 4.2.2 Jelly Bean rooted firmware for the PiPO M8 HD (both 3G and WiFI models) it is based on latest official update published on 2014/03/28. 

( M8HD_1.1.5_update#367_20140328.img / M8HD_software_OTA_3G&WiFi_20140328 )

Build information:

Kernel: Linux version 3.0.36+ (root@alex-System-Product-Name) (gcc version 4.6.x-google 20120106 (prerelease) (GCC) ) #367 SMP PREEMPT Fri Mar 28 09:54:46 CST 2014

Android 4.2.2 JB: rk30sdk/rk30sdk/rk30sdk:4.2.2/JDQ39/eng.root.20140328.095542:eng/opinions-on-teclast-p90hdst-keys

ro.rksdk.version=RK31_ANDROID4.2.2-SDK-v1.04.00

Notes: 

- any update received thru OTA may interfere with our custom firmware, we recommend not to apply any OTA update

Custom firmware features:

• root with latest SuperSU version 1.94 (free version)
• removed most Chinese and unnecessary applications
• Google Play Store fixes so more application are visible/compatible
• updated busybox v1.21.0.git (2012-11-29)
• Unix like init.d boot scripts support, more details on init.d scripts here
• changed permissions on external sdcard to allow write access
• disabled OTA updates (may cause problems, see Notes below)
• increased space for applications (/data partition) to 7 GB
• kernel modules (cifs, tun, lan, serial, xpad) compiled by Oma & Crew RKTablets, thank guys!
• optional ClockworkMod (CWM) Recovery easy install package

Download: kasty-pipo-m8_hd-422-20140328-rooted7.zip

Flash with Rockchip Batch Tool version 1.7, use Restore button.

Please report any problem with this firmware, I can't verify this custom firmware works as I don't have a PIPO M8 HD tablet to test the custom firmware.