For quest Dissension amongst the ranks, when putting on the enchanted Illidari tabard, the disguise does not work/change appearance of character. Killing the crazed colosssus while having the tabard on character does not count for completion either.
Appearance of character should change and killing mob should count for quest count.
Character appearance should change. Killed mob should count for quest tally.
Thank you for the report, the issue with the killcredit already was reported here #5026
The tabard only transforms when equipped in the Eclipsion Fields