You're applying an absolute to this argument where I am saying it is having some effect. Nothing quantifiable but there is some.
The problem is no one knows whether the effect was positive or negative. There is no way to know that.
Also you're INCREASE is being based on something that was suppose to increase all along. TDKR was already projected to outgross the combination of Potter plus Captain America. By a very good margin too.
"Supposed to" is where the problem lies. These projections were wrong...which happens very often (See The Avengers for more proof)...because the obvious factors that indicated TDKR should make less than TDK were ignored. It was always illogical to say TDKR should make more than TDK.
Two Batman movies:
Movie A:
1-Features the Joker. The most popular Batman villain by far. It's not even close. Movies featuring the Joker do better at the box office.
2-Features an amazing performance by the actor playing the Joker. Audiences and critics raved and he was magnetic onscreen. This was known about before the movie was released.
3-Said actor dies tragically before the movie opens which fuels hype, free publicity, and generates morbid curiosity. "His last performance".
4-An RT score in the 90s. Rave reviews in general.
Movie B
1-Features Bane. "Little-known" is putting it mildly. "Who?" is the typical reaction from the public. Catwoman helps...but Batman Returns also featured Catwoman and that didn't help the box office.
2-Little to no advance raves about the actor playing Bane.
3-No tragic death to fuel hype, generate free publicity or morbid curiosity.
4-An RT score in the mid-80s. Less impressive reviews.
No way Movie B should make more....but many believed it anyway.