Nope.
Sandman was involved Uncle Ben's death from the get-go. I wouldn't be surprised if Raimi had been planning that for awhile before Spidey 3. Before Venom came to the movie, revenge was the theme. Vulture was Venom's part, being the one who couldn't forgive. Spidey had ruined his career by exposing him as a fraud in his business or something like that.
Yes, there probably would not be a Symbiote, but other than Eddie Brock/Venom, the story was the way it was with Harry and Sandman.
Which one was unnescessary? Well, I say none. You get rid of one, a theme is ruined. Get rid of Sandman and Spidey's motivation and all the emotion would be gone with the Uncle Ben involvment. Symbiote Spider-Man would have no one besides common crooks. Beat on Harry? Well then we don't get to see Harry be normal again, which really helps make his death more dramatic. Getting rid of Venom would just make the whole Eddie Brock not being able to forgive thing go away. All the characters are tied in a revenge/forgiveness concept, and Eddie was the one who just went with the revenge. He was the most evil of the film, and did quite a bit of damage.
Now, I liked Venom in this movie. Should he have been in it longer? Well if he was going to have to die, yeah. Otherwise they should have let him live. I really like the way they did it. Venom being in a revenge concept is how Venom is really, that's not Vulture. The Symbiote was the way to go in this film. You can say it wasn't well thought out, but after countless viewings and reading the making of book, I really appriciate alot of the care that went into it. It wasn't perfect by any means, I did have a issue here and there, but I thought they took the story in new and interesting ways. It may seem crowded by description, but I believe they balanced it out really well.
