That is, only if you are walking. Most people are too lazy to set it to walk every time they engage a mob, and when you kill an enemy, or if it moves, you will follow and move. Then, defense doesn't even come into play. Nothing wrong with getting defense for melee char, but there's no point in getting excessive amount of it if you cannot play in such a way that utilize it well. Of course, your chance to block is shot to hell as well, but it is usually far easier to get max block. Presumably, if progamers exist in D2, they will use their 300 APM to switch run/walk all the time to maximize its benefits.
However, I don't see too much of a reason for insane defense vs the ubers, they are lvl 110 after all, so they will hit you just because of the lvl difference.