I stole one worker with one DOW; made peace immediately after and didn't DOW a city state again, nor was I at war with any players for the remainder of the game. I was playing a team game with a friend, we had 2 of us on a team, so maybe that counted as two DOWs. My partner also did not DOW a city state, my stealing a worker was the only known act of war in our 90 turn game.
A quick rant:
First, that's just poor programming for a team game if so.
Second, why didn't they just make city states defend their workers, rather than put in these ridiculously punitive penalties for declaring war on a city state? You know, force them to build a warrior first and always move the warrior with the worker. That would be a much better way of going about things than just saying "Well, you declared war on a CS once, you have to completely abandon the strategy of allying them for the rest of the game." Ugh, just awful design.
Last, why didn't they tell me about this in the prompt? I was fine with a permanent -20 resting point with one mercantile CS. I was not fine with a permanent double influence loss with all city states, the worker is not worth that, we would just have reloaded and I wouldn't have taken it. Complete waste of hours of time due to lack of information delivered to the player. Extremely disappointing.
OK, one more point: with all of the other exploits available to accelerate yourself (selling stuff to AI, selling gpt to AI, buying gold and DOW, letting barbs pillage sold luxes, etc) it seems bizarre that they targeted city state worker stealing as an "exploit" to "fix." What about all the other exploits? They are a lot more 'exploity' and less interactive than stealing a worker. Just a bizarre choice for a "fix" in my opinion.