Voidwalker Abyssite evolution rate

Hi, having to post on behalf of someone who has issues accessing the forums

Details:
Attempting to change a clear abyssite into a colorful abyssite by vanquishing the voidwalker monster has yet to yield an abyssite change after 50+ consecutive defeats.
While I appreciate this is a random element to the content, I feel that <2% effective rate may be unintentionally low.

Steps:
Voidwalker NMs were popped in a variety of zones in original and WoTG areas.
Defeat of the monsters is not yielding a colorful abyssite

Date & Time:
27/08/2014 (DD/MM/YYYY) from 15:00 BST to current time.

Frequency:
State how frequent the issue occurs. Please select from the following.
1. Always

Platform:
PC

PC Manufacturer & Model Number:
Lenovo z580

Operating System:
Windows 8

Graphics Card:
Nvidia GT 635M. (+ intel HD 4000)

ISP:
Virgin Media UK.

Type of Internet Connection:
Cable Broadband (WiFi)