I agree that the mission lengths lead to fatigue! Some stuff goes on too long, despite being amazing in its own right all the way through. This can be exacerbated by the order of the missions, like going from the labyrinthine Death's Dominion to the equally winding The Brand.
I wouldn't say the mission goals lack variety - yes, pretty much every mission is a robbery, but 2 of them are tomb raiding, there's breaking into an abandoned mansion, recovering an item you lost, a mission that star...
I don't know about the 4-5 hours playtime, but I've played the mission on Normal and yeah, it took me ~2 hours (though technically I could finish it sooner, I just tried to explore optional areas), so with the additional objectives I can imagine that estimation is correct. The mission perhaps relies on the player collecting the scattered loot a bit too much.
I use the regular FM loader. I went into the cam.mod thing and deleted the semicolon ;
I think it comes with the game. I got Thief off GOG, because I never actually played thief gold. I played the Dark project when I was a kid, and I saw it and that it had new missions and I thought it was cool, besides that I don't know what all the different versions are
I got into fan mission because I saw a step by step video on youtube by easymode on how to install them. I'm pretty bad with comput...