The chance of those extremes does keep the game exciting though. Going for a 4 on a d4 when your opponent has just thrown a 2 on his d10 is edge of the seat time. Although in this example the side with the advantage will rout on that result in a melee say, it cannot be badly damaged by the “inferior” unit as the number of hits would be the difference between the scores. This means that your elite units might have a setback in this situation but are unlikely to be destroyed by a bit of bad luck....
My thoughts on this are well known.
Firstly, combat, especially melee, is never a sure thing and is always a risky business. The all seeing eye in the sky isn't present for real soldiers, perhaps ordered forward over unforeseen bad ground; perhaps with officers and NCOs being killed; general fog of war; the enemy being led by a truly inspirational anonymous hero who turns the tide - like the maid of Saragossa seizing the linstock and firing the cannon after its crew (and her lover) was killed at it, throwing back the French; etc. Generals seek to stack the odds - D12 Vs D4 - but it's never a sure thing.
Secondly, it's more elegant than the bucket of dice Vs bucket of saving throw approach. One dice each, now that's clean. Furthermore, the opposed dice mechanism always keeps both players 'in play' at all the moments of decision and combat resolution.
Just my two penneth worth. No more valuable than anyone else's.