At those ranges even the more accurate rounds demand adjustments. As you your self pointed out. And even with more conventional rounds it would still need ranging and adjustment at those ranges.
Until technologies like the XACTO come online and advanced sniper fire control systems making shots past a mile or even two is not a mundane thing here wolf. No ordinary person is going to pull it off. It takes skill, training, tools, support and a good deal of chance.
I do some shooting myself, so I have some idea of how hard such shots are to pull off, and how much of it is down to chance and luck no matter how good you are. Which is precisely why I am dubious about the real life value of such party trick shots.
Elite snipers making impossible shots and/or terrorising entire companies of enemy troops might be the stuff of Hollywood wet dreams and computer games, but in real life, against a near-peer foe who has well trained and well equipped soldiers and snipers of their own, the value of snipers are going to be massively reduced.
Sure if you absolutely need to be sure of the event call in artillery or better yet a airstrike. However keep in mind the cost of that and that artillery also has to range. And consider that in some situations using a howitzer is just not a option.
The Kyle shot case in point the spotter used by the insurgents was on the balcony of a hospital.
Just take a look at the news paper today and we see the outcome of what would have happened if Kyle had not been the reaction but an airstrike or artillery barrage.
I never said snipers would be useless, and there will be a few instances where they will be useful, such as your example showed. But they are the exception, rather than the rule, especially if there are enemy snipers.
As soon as you face competent enemy snipers, your own snipers have to play a very different game.
Rather than find the best vantage point possible and shot all day from that perfect spot, they are going to have to instead look for less obvious nests, which invariably will mean they won't have as commanding a field of view, and should also change locations after every few shots (after every shot if there are good enemy snipers operating in the area).
In that respect, snipers are very important, but mainly as a means of countering, or at a minimum, massively reducing the effectiveness of enemy snipers.
You have made the point if armored personal what about armored shelters. Pill boxes designed to resist bombardment.
Anything able to withstand artillery and/or air strikes would also be proof against a sniper bullet, even 20mm ones.
I do not downplay or discount the value and capabilities of good, world class snipers. But I am also aware of their limitations.
Snipers are more of a asymmetrical weapon, able to effectively hound and harass a superior enemy force with a minimal commitment of men and resources on your part. But they are not that great at the kinds of fast paced fluid environment of a full fledged armoured clash.
I would place heavy emphasis on snipers for elite forces like scout recon, paratroopers, aircav, special forces and the like, but for frontline troops, especially mechanised infantry, designated marksmen with semi-autos are far more effective and cost effective in terms of allocation of training and resources.
Come up against enemy snipers? Ask your attached tanker buddies to send a shell his way, or hop in your APC/IFV and blast him with your 20/30mm or drive up until your designated marksmen have range.