The main problem for me in the OP's thread is mentioning the wish for a challenge and at the same time sneak attacks as problem. What seems to be the problem is the abuse of game mechanics meant differently or designed poorly. There is no need for a higher difficulty for my taste but a need for a 5e game with normal abilities and hp, restricted loot, no abundance of gadgets and no easy way to abuse game mechanics. Probably impossible to do with decent effort, I fear.
