Vic actually has a lot of personality traits that could be turned to dangerous ends in Slytherin, but he's too self-sacrificing and his ambition is actually a side-effect of more pressing concerns (he doesn't crave power for power's sake).
Even though he's a lifelong scholar, the pursuit of knowledge doesn't define his life enough to really do well in Ravenclaw. He could never give up being a hero to be a teacher and is much more likely to do the opposite, so this really doesn't work as his primary house.
Vic is definitely loyal and hardworking, but quiet service isn't how he views his contributions to others. He needs something bigger and bolder to spice up those long doldrums of hard patient work every now and then that most Hufflepuffs don't mind.
Vic's a Gryffindor. He's careful and smart enough to plan whenever he has the opportunity, but he'll rush headlong into danger if he thinks he has a chance to save someone. He can pull himself back from foolish actions if it means saving more people, but he will always act to save others. His belief in true love and its connection to heroism are essentially his most defining features.
The Scarf of Sexual Preference says: What Comes After "Intense?"