Can you please stop looking at things in vacuum
I do not believe I am, nor do I appreciate that assumption. I'll explain further below.
Everything comes with a price.
In this case you are basically trading a potential edge to remove a Minor Action for your opponent.
In most situations I would say that this is a pretty Good trade-off ;-)
Most everything, sure. But those prices vary significantly. Lets leave
your vacuum for a moment, and consider the following scenarios.
1). Human with body 3, armor jacket vs. sniper.
In this scenario, I agree with you 100%. His body and armor wasn't going to help him anyhow, the scope is irrelevant. Forcing the attacker to spend his minor action aiming is, by itself, a better trade than the victim gaining an edge. That minor action cost may or may not be worth it, depending on the other scenarios in the combat, though. Did he lose a second attack to aim? Did he need those additional actions to dodge or take cover? Lot of variables, but the likely outcome is as you assessed.
2). Big troll body 10, titanium bone lacing, 2 cyberlimbs, full body armor with helmet, final DR 23 vs. sniper.
In this scenario, I fully disagree with you on all points. The troll spent significant resources in essence and money to ensure he would generate edge when attacked. Having that trumped by a chump change trinket and a minor action is not only unbalanced, it's insulting. Again, the cost of that minor action is subjective based on additional circumstances present, but it is almost certainly in favor of the sniper. Not really because of the single point of edge, but because the troll spent his character generation resources on something that did nothing for him, while you sniper spent his on other things that function for him appropriately.
While you look at it as edge vs. minor action, I look at is as 3.5 points of essence and 100,000 nuyen vs. chump change and a minor action.
All of these figures are still beside the point of the elements you cannot mathematically measure, such as uninspired, unfun, unbalanced, nonsensical, ect.
1. If you are within his optimal range category then odds are you would not get a tactical advantage while being hit anyway (at this range the attacker often get a base AR of 10-12 or so, not counting bonuses from smartgun systems or vision magnifications).
Odds based on what? Literally all it takes to deny the vast majority of attackers (with AR 14 being near top end before add ons) edge gain on attack is a max body dwarf, ork, or troll in an armored jacket. That is before even trying.
2. You might secure your two edge from other sources, anyway
Sure, you're not wrong there. But that hardly excuses the armor AR/DR system from needing to function well because you can get it from other parts of the rules.