I have seen many arguments online about the necessity of back up sights on a rifle using optics. The general concensious seems to be that they are needed on military rifles, but not on civilian rifles. This is not the case.
In the military people work in teams and are almost never alone. Should a rifle go down it is not really an issue as you still have many other people capable of continuing the fight. For the civilian and the police officer this is often not the same. If someone wakes up in their home and finds the battery dead in their reflex sighted rifle it helps to have iron sights. However if a Marine’s optics fails, he is only reducing his squads fighting ability by 1/13 its firepower.
So do you need back up irons? First needs to consider if the rifle is a toy, or a tool for fighting. If it is a toy, back up sights are not necessary. If it is a fighting tool, look at its role and how it is set up. If you are running battery powered optics or magnified optics on quick detach mounts, I would suggest back up sights. So if you need to use a wrench to remove your optic, back up sights may not be practical for you and you may be better off switching to a different weapon.
“Damn, the batteries are dead.” Is not an uncommon saying at the range I work at. Not only among cheap optics with poor battery life, but often about Eotechs. Batteries discharge, cheap batteries and cheap optics drain even faster. Even the best optics can be broken. On the range this is just an annoyance, for the Soldier or Marine it means that their buddies will have to take up the slack. However if you, as a lone civilian or law enforcement officer, have this happen in the fight, the results can be costly.
I highly recommend back up sights on the individuals fighting rifle. If you are fighting by your self, being able to keep your weapon in the fight is crucial.
On that note, also make sure to keep your back up sights zeroed.