You can get some info on the kishin nerf by searching for the term 'kishin' in the FAQ thread
here. I believe it's most likely a hidden debuff as it applies to the map that kishin is activated in.
As for Kanna being the best meso farmer... probably not. I believe a class' ability to clear a map quickly/efficiently matters the most in AriesMS for farming. Also there are mainly three activities that make players money in this server in which class matters. Those are bossing, general map farming, and monster park. You can search around forums for answers to what classes are better at those activities than others.
For instance, people always recommend Hayato and Wind Archer for farming monster park as Hayato has high mobility and Wind Archer can clear maps easily.
As for classes with high mobbing ability, I prefer NL. Someone can correct me on this, but I believe Wind Archers, Dawn Warriors, and I/L mages have high mobbing ability as well.