I didn't address the screen time of the stone giants. Only that they did exist in the book, and that they were a motivation along with the miserable weather for the company to seek refuge. I certainly didn't defend the scene. In fact, if I were making any assessment of that scene, I'd agree with your point, and further say it would be the very definition of the 'bloat' of turning this into three films. It was clumsy, not very entertaining, and not even all that visually stunning of a scene.
I'd take that a step further and say that I didn't care for many of the CGI scenes in the movie aside from the stone giants. The Great Goblin and Azog were both shoddy and looked obviously CGI'ed, which is a stark contrast to LotR, where the only CGI scene that really stuck out as obvious CGI was Legolas mounting his horse in Two Towers.
As for Tom Bombadil, I've never had a problem with him being excluded from LotR. I get his place in canon and all, but he would have made the film version of Radagast look normal. And you seem to have had a problem with Radagast as he was portrayed, so I'm not sure you'd have wanted Bombadil in a screen version of LotR either. It was much more bothersome to me that the Gray Company was excluded from LotR than Tom Bombadil.