It's not 100%, I've had many traps fail to be placed in the past with 100% mastery. I do think poisoners and trappers need a boost.

Also, the poisoners, level 72 KO with full mastery is resisted by some class/races 100%

Also, poisoners don't get even get a PK credit if the enemy dies to poison, hence I had 15 pk wins? even though many dies to emetic grenades and other poison methods..

What do you feel about flyto/peck or undead full immunity to certain weapon specs/invokers immune to elemental? That is a true 100% success rate