Arsenal had bad record when facing Bayern Munich in last several matches before on Champion League, season 2016/17 its the last time participating by Arsenal and defeating many goals by Bayern on first and second leg matches when Mikel Arteta still as players. Currently its not matter with how many matches Bayern Munich leaded head to head, both teams performance in Champion League and domestic league this season drastically difference, Arsenal had better performance lead the top position in domestic league and Bayern Munich loss their performance and this season seems can't be the Bundesliga winner.
Arsenal this time has chance for eliminating Bayern Munich in quarter final round, not matter with how many matches Bayern Munich lead head to head but Arsenal currently has better performance than Bayern.
Arsenal impressive record could have failed at the hands of Bayern Munich, the intensity of competition in the Champions League is much different from the domestic league. Bayern Munich progressed smoothly in the group stage, and they recorded only one defeat in the round of 16. Meanwhile, Arsenal have recorded two defeats so far, once in the group stage and once in the round of 16. So in the Champions League, Bayern Munich has a better winning record than Arsenal, while in the domestic league Arsenal is much better than Bayern Munich.
I think now that Arsenal knows they are going to play against Bayern Munich, you are worried because of the past games because now there is a chance for Bayern Munich to score five goals again against Arsenal. Except for the recent fiend match they had in ~5 years ago in which Arsenal won the game with a 2-1 result. In the other games they had, Bayern Munich won the game with a 5-1 result, and scoring five goals is not something normal at all.
Now Arsenal is not in a bad situation Bayern Munich is under pressure because of losing the Bundesliga title and they have to beat Arsenal, I'm waiting to see how Bayern Munich and Tuchel can perform against Arsenal.