I don't think SM3 needed 2 films, honestly. I think doing Venom at the climax could have worked. But, I think Brock needed more scenes (like the one they FILMED with him visiting Gwen after he was fired and finding out about Parker). Also Gwen should have been kidnapped. Not MJ AGAIN! Yes, MJ and Peter have a personal connection, but they could have had MJ come to the battle site after Spider-Man was already there getting thrashed. Had Venom kidnapped Gwen, it would have developed HIS character better. Something he desperately needed.
I think those 2 basic changes make Venom better.