Lyxen
Great Old One
If you stick your head out (and eventually your weapon) in the same spot multiple times in a row, enemies will know it is coming, and will see your head before you make the attack, even though you where hidden before hand.
If, on the other hand, you can find multiple spots to "stick your head out", that won't work.
Exactly, this is what it's all about, being really unpredictable, making it fun, inventive, imaginative, clever tactically but in the gaming world, not on the board of a board game.
Of course, the rogue will get advantage on his first attack from stealth, but after that, he will change positions, hide behind something else, attack from a different angle.
And if he can't, well, it's not impossible, just much harder to get the drop on an opponent. Unless, of course, the opponent is very dumb and cannot figure it out, which then shifts into actual roleplaying on the battlefield, and playing characters and adversaries with their strengths and weaknesses, mental and physical, telling a story and making it feel real, not cardboardy.