Well, to be fair with Begins, they made it pretty obvious in the beginning that Ducard/Al-Ghul was a villain. Whereas in Dark Knight, even though we were familiar with Dent's history in the Batman lore, it wasn't obvious that he was going to be Two-face.
I don't know, I didn't really care about that like you did. A bit Spider-man 3 like, sure, but way more compelling.
Two-face wasn't a big villain in the dark knight, he was just another part of Joker's plan, or the main theme throughout the movie. All that really mattered was that he was a really good guy that turned into a bad guy. I mean, in the comics Joker tried to do the same thing to Gordon and even cripples his daughter, but Gordon didn't take none of that shit. And in the end when Batman covers for Harvey crimes, he does it to hide the Joker's victory. It's not like he became the two-face of the comics where he's a mob boss or anything.
If anything stood out as completely awful, it was that entire boat scene. Something like that was needed, but it could have done without being so boring; just keep Deebo.
Same with Batman Begins, btw; all the villains were connected from the start. Ra's was more or less playing Crane and Falcone like chumps, the latter who partly responsible for Ra's going after Gotham in the first place.
Spider-Man 3 literally pulled Venom out of its ass. Hell, it pulled both villains out of its ass. Good jon rewriting the Uncle Ben's death to have a villain that just kinda floats away. wait, green goblin on a surfboard is there at one point, but he's an anti-hero I guess because he lame ass butler randomly tells him that his father done killed himself. ah wahtever.