It's been a while since I watched FSN - but from what I remember, Rin seems to be more Tsun than Dere. I like Rin, but I find her way too cold and objective to the point of being unattainable. That is, aside from UBW.
The reason I fell in love with Tsudere characters, a definite 5 for me and my most favorite female anime character of all time in a way, a biased vote for me here. though it's truly fleshed out in the visual novel esp. unlimited blade works arc.
i don't understand how she is getting so high scores, but saber isn't. imo, saber is way more tsundere than rin. she was at no point that I can remember hostile towards the mc. maybe aloof, but I wouldn't say to the tsuntsun lvl.
2/5 for me
although with that said, I think she is a very god character and I even liked her more than saber for a lot of the anime. (never played the game)