I'm not sure when the "DPS dagger-wielding thief/rogue" archetype first appeared, but regardless of its origins, I detest it. If you're wearing cloth pajamas or a leather jerkin and are carrying only a dagger and perhaps a bow/crossbow, the last place you want to be is anywhere near a battlefield facing properly trained, armed, and armored opponents, let alone wild animals or mythological creatures. That's not to say that thieves/rogues shouldn't be capable of assisting their party with ranged weapons or by ambushing an enemy before fleeing back to the rear rank, but their expertise shouldn't lie in direct combat. Their damage potential is highly situational or supplemental. Their primary purpose is to scale walls, spot and disarm traps, pick locks, sneak around stealing things, carry out silent assassinations, perhaps work people over with their silver tongue, and so on.
The Lord of the Rings trilogy/prequel, early D&D, and dungeon crawler cRPGs respected this notion that burglars, thieves and rogues weren't mythical ninja-like creatures, and required the protection of trained warriors in their party if they expected to survive. P:E will allow mid-combat backstabs and other such rubbish, if I recall correctly, which... is annoying, but expected.