Originally Posted by FastRedPonyCar
[...]I hit the 100 level character cap and was practically invicible at that point and had to use custom made maps with nothing but boss monsters to provide a challenge.[...]
But that's ultimately the problem of all action-RPG games I've ever played, even the nearly perfect Diablo II suffers from it. There's always
eventually going to be a point at which your character(s) has "the best" (or "most efficient" in regard to specific situations or counter-attacks for specific enemies) equipment and skills build, and then you pretty much beat all foes on your path with barely any (or none at all) challenge, with sometimes a few exceptions here and there (for instance, in Diablo II's case, exceptions would generally be Stygian Dolls, Souls, and packs of Blood Lords, but even they don't have a chance in face of some specific character builds, and as of patch 1.13 our good old Oblivion Knights became a bunch of sissies since they lost their Iron Maiden advantage against melee characters). It's certainly true for Torchlight since that game is very lighthearted and isn't very serious, just at the image of its balance, and it's also true for Titan Quest and Sacred/Sacred 2.
I presume that it will also be the case with Diablo III.