Dragon Flame Skill Does Not Work For Kravras

The Dragon Flame Skill DOES NOT WORK for Kravras. I spent over $300 to get this skill specifically for it's usage with Kravras since I play a bowmen set up, and in over 500 battles (and yes, I went through 500 battle reports) it has not triggered the special effect one single time. I have seen it trigger with those using the skill with Sinara, but it does not work with Kravras even though that's how it is advertised.