You know... Thats what back up sights are for right? Bad things happen, and you are not completely screwed.
Its like getting in a car race with high stakes and being offered a modern corvette to drive, and saying... "Nah... I will stick to this old caprice, its reliable and never let me down before. That new fangled corvette with all its gizmos might break down."
The chances of such a thing are extremely low. When you place bets, you place them on the most likely to win outcome, not the lowest.
"99.99% of the time a quality red dot will work great and give me a definite advantage over iron sights for speed at close range, but it might break that 0.01% of the time, so I better stick with iron sights only."
That makes no sense at all. You don't handicap yourself on an extremely low chance that doing so would be better in the right situation.
Iron sights can break too. Especially one that mount on typical flat top uppers. The old carry handle style are about the toughest on the whole, but not invulnerable.
An ACOG or an aimpoint comp is going to be about as tough as a good set of irons are.
An Aimpoint has a battery life measured in years... Turn it on and leave it on. You don't have to worry about batteries at all. Swap the battery once a year or two for peace of mind, and carry on. I believe the Comp m4 can get 8 years out of a single AA lithium battery.
If you can't buy a single battery and have it sitting around ready just in case... Something is wrong.
So if you buy a quality red dot sight with battery life measured in years... Like a Comp m4, T2, or MRO with a QD mount... And keep a spare battery on hand just for the optic... just in case... AND you have a set of quality backup iron sights on the rifle... You will be fine. (in fact the genuine MBUS sights are excellent low cost options for backups, and modern batteries have shelf lives of 10 years.) Should the unlikely happen and the optic go down, pop it off and run the backup sight.
I like shooting irons from time to time. Its good to keep in practice... But for a rifle used for defense, a red dot is what you want. For a SHTF rifle, red dot there too... With a spare battery in the grip.
If you are really worried about batteries, then an AGOG... the 1.5x model is handy for close range. Not quite a red dot though.
If you just want irons because you like them, and defense isn't a concern... then go for it.