It could be argued, a reasonable player won't exploit the system to find powerful unintended combos. Alas, this is not the case.
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.
All I need is the word "weapon" in the correct place and I'll be happy.
Every time someone mentions those cheeseball builds, that are RAW legal, stupidly overpowered and make no sense what-so-ever, yet people keep playing them because they are hyper effectivre, I want to vomit.I'm looking forward to a Daggermaster nerf. I don't mind optimization, but the ever-popular Sorcerer/Rogue--Daggermaster (of which we have one in the Paragon game I'm playing in) feels like a bug exploit, which irritates me.
All I need is the word "weapon" in the correct place and I'll be happy.
This. Daggermaster is fine as long as you're made to stick with the d4 for your damage die.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.