Sorry but that's just ridiculous in both directions. You assume that on one hand, average players know beforehand whether their build is broken or not, yet, there are many players who simply don't have that amount of system mastery. On the other hand, you assume that optimizers can see into the future and can accurately predict what will be nerfed and what won't. The actual game doesn't work like that.
In our group, we've been largely untouched by errata and updates, but it does happen. One was a jagged weapon, that had no save on the ongoing crit damage pre-errata, and the other was a Veteran's Armor. The DM put one in the treasure, and my Ranger used it to attack with Jaws of the Wolf twice in one combat. 80 damage is pretty good for 2nd level... That's when I as a player told the DM that this item was nerfed two or three weeks before.