Mirror image suffers a major issue though. It only lasts 1 minute and takes a pretty significant number of attacks to exhaust its duplicates on average.
In our adventure day of 8 3 round encounters I’m not sure that mirror image is a particularly good defensive investment, even when it can be precast.
First, shouldn't the combats be 3-5 rounds average not just the low end 3?
Second, by 11th level many monsters have multiple attacks so the wizard getting attacked/hit multiple times in a round is common. I don't think expecting 3 hits in 3 (or more) rounds is at all unusual.
Mirror image soaks up the damage here AND, as importantly, avoids the need for a concentration check. This is a solid investment for a 2nd level slot - especially if precast.