Here's my two cents on the matter.

Sephiroth is suposed to be portrayed as some "invincible" character at this point in the game - That's why when the flasback ends abruptly Cloud automaically decides that he couldn't possibly have won against Sephiroth, because he was...Sephiroth.

The main focus on that scene is that Sephiroth is back, Rufus just happens to arrive at that time, but Aeris and Red XIII's coments are more focused on Sephiroth, I think. It matches him a lot better, I don't think Rufus really has a reputaition like that.

Barret and Tifa's lines DO refer to Rufus, however, but that kind of makes sense - Barret is obviously more focused on Shinra, he probably doesn't even care about Sephiroth at this point - his lines are "I hear he's been asigned somewere else", obviously about Rufus.

Tifa's lines are "I wonder what kind of person he is", that can't be about Sephiroth - she knows what kind of person he is...