I do want to add one thing that the monk 6/ rogue 5 brings to the table and that is shadow step, a bonus action teleport in dim light or darkness that makes the first attack after the teleport advantage. Doesn't cost chi, and the only limitation is a bonus action so once per round. Combine that with stunning strikes and the monk combo can create its own advantage on attacks in a way that rogues can't, and shadow step can also be used defensively after an attack in dim light to teleport up to 60' away with no chance of an attack of opportunity. A 6th level monk base movement of 45'(40' small size/50 wood elf) a round and you have a class that in dim light or darkness can move 105' (100'/110') without using an action or 150' (145'/155') using the dash action, again burning no resources other than actions/bonus actions to do so. Shadow arts allows for pass with out a trace and the with the rogue levels you can use expertise on stealth make you insanely hard to spot when you are sneaking making you an ambush master, which is why you take the assassin subclass from rogue and become a ninja. Wood elf is pretty much a perfect pick for this because you get increased base movement, dark vision, and mask of the wild for even more stealth. Halfling would also be a fantastic pick with +2 dex, lucky and the ability to hide standing behind taller people, but the loss of dark vision could be less than optimal depending on how Larian deals with short rests (if it's like table top then it is no problem, just cast dark vision before a short rest and it lasts 8 hours and you get your chi back after the rest). Like I said it is all trade offs, but I personally feel that the gains more than offset the losses depending on how Larian sets up the environment.
