The modern combat helmet was designed primarily to shield troops hunkering down in trenches from overhead fragments, at least until they can roll on over to the nearest shelter where the airburst rounds are next to useless.
Helmets save lives... they are not perfect, but look at any conflict where one side wore helmets all he time and the other side didn't and you will see a marked difference in dead and injured... unfortunately in some armies a helmet is considered cowardly, yet the most lethal wounds you can get in war are head injuries and upper chest injuries... wearing body armour for your upper body and a helmet to protect your head greatly reduces fatalities and serious injuries in any type of combat.
If you could take out troops in trenches with artillery then why was WWI such a stalemate and why were tanks invented...
Why are Russian tanks better protected?
the article you quote says...
The problem relates to how the tanks' ammunition is stored. Unlike modern Western tanks, Russian ones carry multiple shells within their turrets.
Soviet tanks store their ammo beneath their turrets where the ammo itself is unlikely to get hit... modern western tanks store their ammo in the hull and rear turret bustle and are actually easier to hit in combat as shown when facing enemies provided with modern anti armour weapons.
In the defence the Leopard hull storage was not so big a problem. In the offensive...... that was/is another story....
Another factor is that in the middle east most opponents of the west were familiar with Soviet tanks and where their ammo was but not so familiar with western tanks. Once they started to realise the rear of the Abrams turret is not heavily armoured and is full of ammo then you started to see more vehicles being taken out... and whether it blows the turret off or not doesn't matter... an ammo explosion will kill the crew if they are still in the vehicle.
Normal armour penetrations will start fires and disable the vehicle at which point the crew don't press F to repair things... they normally bail out of the tank and find cover... it normally takes a few minutes for the fire to get hold and get to a temperature to set off the ammo and fuel.
id be interested to see how you would feel if you were witrh body armor, in a slit trench, and a 152mm shell was exploding 10m above you. I doubt you'll end upwith just some bruises.
The idea of a slit trench is to reduce the number of effective angles that fragments can actually hit you when you are crouching down out of line of sight... to be effective the shell would need to explode directly overhead... 5 metres either side would not be good enough... which means an impacting shell with that level of accuracy would be even more effective...
If airburst ammo was so effective why even bother to dig trenches at all?
Airburst ammo is much more effective than impact fused ammo, in the right conditions.
Enemy hiding in a building and you fire the airburst 40mm under barrel grenades and the small charge that blows the grenade up into the air would blow it away from the wall or door of the building making the explosive effect of the main charge less effective. The standard impact grenade might blow open a weak door or damage it and would be more effective.
A slit trench with top cover would make airburst rounds rather less effective too... for not a lot of extra work.
BTW I wouldn't want to be shot with a .22LR bullet, but that does not make it an effective standard rifle bullet.