Re: Overquest - What if the good guys had already lost?
I looked over the Time Thief, and while better than the Rogue it's not that great unfortunately. It has limited combat ability compared even to the rogue, and while the utility is nice, it doesn't do that much.
Rogue type characters are fairly easy to make without being rogues though. The best first party rogue type characters can vary depending on what sort of roguish characters one wants to be. Rangers are the best stealth characters in the game, and make excellent assassins, bounty hunters, and so forth. They're strong in melee, and of all martial characters have the most versatile spell list, and don't have any aspect of the game they don't touch on, making them excellent for people who want to learn the game.
Bards make excellent con artists, rakes, thieves and so forth and are very powerful characters. They have the most skill points and are the best at skills overall in the game, due to their various class features, and are very strong in melee combat as well. They're not just buff bots, though their ability to buff is strong.
Inquistors are like the divine version of Bards. They're not quite as good at skills but are pretty decent at several, and are the best intimidators in the game, even better than Anti-Paadins. They're powerful combatants and have many means to detect and function as bounty hunters of the faiths and other roles.
Investigators are the second best skill characters, being able to add extra dice rolls to many skills. Their combat style is a little complicated but potent and they've aces to msot of the Alchemists kit which is potent. They'll only be able to self buff but when it comes to skills they're hard to beat and they're effective combatants.
Alchemists aren't the best at skills, but like the Investigator they get the most skill points due to being int casters with more than 2+Int. They're powerful jack of all trades, having access to strong nukes via bombs, powerful buffs via extracts and mutagens, good utility via extracts and so forth. But most importantly is the alchemist is the only class who can make poison worth a damn.
Slayer is like a worse ranger but it's not the worst option you can take.
Vigilantes have some derp mechanics but their class features would be very useful in a campaign such as this.
Mesmerists are sort of like bards, but rather than buffing friends, they debuff enemies.
Occultists are great for archeologist type rogues who do their tricks via relics they've stolen and such.
Going into third party stuff, if you're really set on time stuff, the Stalker from Path of War is a rogue/monk/ninja type of character who get's access to the combat style known as Riven Hourglass, which is based around time manipulation. Even without doing so they're quite potent combatants who are mobile and have good defensive qualities.