The death of Dong Zhuo is not triggered by Diao Chan event.

MTU's concubine mode seems to replace the original event (giving Diao Chan to Lv Bu or not) by choosing to marry Diao Chan as a concubine or not in the next turn after She joins (if you accept Wang Yun's offer in the previous turn).

No matter which choice of the concubine event I made (marry or not), Dong Zhuo's death would not be triggered in the next turn because there is no event of giving Diao Chan to Lv Bu or not in the previous turn.

So it follows as 1)Accept Wang Yun's offer. 2)Marry Diao Chan as a concubine. 3) No event of giving Diao Chan to Lv Bu pops out. 4) No death of Dong Zhuo by Lv Bu pops out. 5) 20 turns later nothing happens as well.

I therefore suspect that the event of giving Lv Bu Diao Chan is replaced by marrying Diao Chan as a concubine of MTU.

I have checked all the modes I use. None of them seems to prevent this event from happening hence I believe MTU's concubine mode causes that.