This would all be one class with 3 different masteries - just for inspiration.
Alchemist - Coy passive trickster. Class specific item drop interactions. Different kinds of unique potions would drop give personal or group bonuses. Farming / looting perks. Passive tree would be split between buffs and de-buffs. possible coop focus?
Monk - no weapons (glove bonus) / melee fighter / health sustain.
Passive tree would be split between “Light and dark” heal / sacrifice (melee projectiles?)
Samurai - (if we cant have one elsewhere 
) 2-hander evasion movement skills and “combos” chaining certain skills results in different bonuses (Similar to Runic invocation but between skills instead of a single one) OR using skills in response to certain types enemy attacks gives bonuses ie: skills have different effects depending on how they are used. (this would be akin to the runemaster as a sort of “cerebral melee”)