I feel you, bro. I'm even using Marik everytime an LD (any level) pops up in Duel World in the hope to get this skill. No luck :/
The same goes for Yugi/Joey/Pegasus exclusive skills, while strangely I got every skill for Bakura.
I've been trying to get high duel assessment when fighting against marik but he's in this suicidal spree with his shadow game skill... I can't get enough turns to get all the cards I need to boost my Duel Assessment :(... any suggestions? I have to kill his monsters otherwise he will summon "masked beast des gardius" and I surely want to prevent that from happening, but while I kill his monsters more LP will be discounted to him while playing and he would end up defeated because of the skill and not my dueling >_>