Slytherin was always under thought out. Their guiding virtue was ambition but none of them seemed to have more than a base understanding of it. I wanted to see the genuinely nice and honest Slytherin character because she was smart enough to know that friends would advance her ambitions more than enemies and the truth was easier to keep straight than lies. I wanted to see them networking and alliance building. I wanted to see the character who stepped in to stop bullies because they knew that might earn them favors. But we didn't really get that.
What we did get was the never-ending blood feud between Gryffindor. The shortsighted ambitious house and the hot headed charge off into battle house.
Which leaves, comfortably below the radar, the "Learn things so that we can actually be competent and form decent plans" house and the "We don't care about innate abilities, we work hard and get results based on our own merits," house.
The thinkers and the doers. Teamed up they should be unstoppable. And why shouldn't they team up? When Harry Potter starts it's been ten years since the last time anyone heard of wizard-Hitler. Potentially rocks fell and he died. But potentially he's been in hiding and plotting his comeback for ten years. People who were know supporters were about to use political leverage to get out of punishment and be falsely declared innocent. His entire power structure is intact, was welcomed back into the world of lawful magic users, and has infiltrated it like whoa. Gryffindor doesn't have anyone to charge into battle against. Slytherin doesn't have any clear path for their ambitions. But if you're Ravinclaw then this is a mystery that needs to be studied. If you're Hufflepuff there's work left to be done.
Which really means that, when you think about it, the ending should have been:
Ravenclaw spokesstudent: We made a plan.
Hufflepuff spokesstudent: And we implemented it.
*The world is saved*
All of the main characters: Huh?