Trickster Question

[Narvait]

So, my Romuva king grows into adulthood. He is a perfect warrior type - brawny, brave, stubborn and temperate. He becomes brilliant strategist with 20+ martial.
A guy is born to lead armies and must be role played like this.

Any leadership trait would have worked. Any, but... Trickster!?

So, how does this +/-30% thing work? What does it impact? This Clever Ambush unlock does not match my HI rich army well. Should I put him on flank with us much LI as possible?

 

[Narvait]

Really, any advice or experience (positive or negative) with trickster is welcome.
Based on previous read it looks like it is the worst ever trait to have on your commander. Since this randomization is absolutely unnecessary and may hurt you more than help. Am I right in that thinking?