Kragnos Warmaster ability explicitely specify he can be include, which supersede BT rule. Gorddrack no. An email from GW is not official FAQ.
Also, at the top of the article:
EDIT: after talking to Declan and others at Woehammer, they disagree that he can be included and believe this still needs clarification with the FAQ team at GW due to the below images from the Battletome.
So I would not count on that (even if i would love it too )