Wow. I'm just ... wow. Half the point of the rogue is its utility. That's where like most of the fun is. I can't even imagine being at a table with players who would berate you for not maximizing DPS in a roleplaying game. When I'm at the table with my dice how much damage I can squeeze out is the last thing on my list of character building.
Depends on the table /shrug. Some are combat, some are RP. Ive DMed games where the players didn't get into a single combat for 5 sessions. Also had a single encounter run 7 hours. Well rounded is usually a good way to go, or at least target specific things because you know your DM likes to torment you and you decide to foil their nefarious plots. In a game like this though, that performance expertise is likely to crop up less than in a game where a DM puts things in that would require performance because they like your character and want you to have fun.