I'll agree with you on the arousal Hulk-out (which honestly is hilarious if you picture that in your head

t
but if you remember when the heart rate change was used, it was always in instances of extreme danger or instances that would in effect mimic anger. For me, that makes the Hulk all the more threatening of a presence for Banner to have to deal with and in effect, want to get rid of. He not only has to worry about Hulking out when angry, but also in other moments of extreme stress and anxiety. I wouldn't say extreme cardiovascular exercise would trigger since when we did see evidence of that in the film, it was Banner running from a strike team trying to take him in, obviously causing him a lot of stress/anger/anxiety.
Again, the film very clearly established Banner as trying to control that side of him by intense training and then ultimately at the end, when he accepts the Hulk as an alternate side to his persona, he can then trigger a Hulk out of his own fruition. It's really pretty intriguing if you think about it. So now we have a Banner that doesn't have to worry about Hulking out through fear/stress/anxiety, but only when he's truly angered. I think it was important to see that evolution take place since obviously Banner couldn't control this thing from the get-go.
Then why did I clearly see that duality without Hulk saying anything? You see the two extremes very clearly personified. Banner is intelligent and articulate and Hulk is not. The two personas are largely at odds with one another. As far as the movie universe is concerned, the Hulk is still a fairly new creature so it makes sense that he wouldn't be able to form coherent sentences right away. I'm ok with Hulk speaking, but I think it was important to understand that he really isn't able to all at once. As Banner learns to control and understand the Hulk, so to does the Hulk start to understand humanity and where his place in all of it is.
I never thought at any point in TIH that the Hulk was simply a giant special effect. He had plenty of character and showed it well. Just because he didn't speak as much doesn't mean he was void of emotion and feeling.
We're obviously going to be seeing a talking Hulk soon, but it's very important I think, for the audience to see that evolution.