It's more like 5/100 would say they have lag problems. Most lag only occurs in high grifts, which the majority of players don't do.
And why assume it's as simple to fix as you think it is? Sure it would be nice if it was fixed, but this is most likely out of the developers (I'm talking about the guys who code the game) hands. Software development (including maintenance and upgrades etc) isn't as simple as "here's a problem, fix it!". Many factors dictate whether a bug or feature is fixed/implemented.
As a side note, if you believe that what you have purchased it "broken", ask for a refund. If you purchased this online through the Blizzard store they may refund you (this worked for someone I know).