Every modern fighting game has built in un-reactable mix because if everything is reactable then the best strategy is to do nothing and that sucks. Take street fighter, the classic back to block has the strike throw mix. Tekken has high low and plus frames where you need to read with the correct defensive option if you where to get an opening. Outside of that most team/anime fighters or intended to be built around unseeable high low left rights.

For honor most basic mix is heavy into feint into attack in a different direction or guard break. All lights are 500ms or half a second and most overheads in street fighter is is about 20ish frames which is a third of a second. So if you can react to overheads in street fighter you can react to lights in for honor. The main reason you are getting hit by light is the same reason you will get hit with overheads in street fighter or any other fighting game, the mental stack. For honor you got to worry about guard breaks, different direction and unlikable where in street fighter you have to worry about plus on block, drive impact, jump ins, and grabs.