There's something really endearing about this trio, isn't there? 3 very different people but they complement each other so well.
To think Mario and Corin nominated each other a couple of times early on in the series. Funny how opinions change over the weeks. I forget her reasons for nominating him but he picked her for her lack of conversation. Now they're gassing away like a pair of old fishwives!
I've always looked at Mario and Corin as the emotional backbone of the house (a job Dave's tried to muscle in on, grrr

). Then when Sam came in they were the 2 who were most vocal about letting bygones be bygones and giving him a fresh start. I think without that Sam might just have been more vindictive and shown less of his nicely funny side.
It would be a poorer final without all 3 of them.