I'd suggest that Rochus is more of a defensive baseliner, not offensive.
I was also wondering about Seppi...I'm more inclined to say he's a defensive baseliner.
One that has me stumped is Benneteau - he doesn't strike me as being a true offensive baseliner; he can counterpunch effectively and has a relatively good net game. But I suppose he doesn't volley often enough to warrant being labelled anything other than a baseliner.
Oli Rochus isn't a defensive baseliner, he is a better version of Dudi Sela.
Benneteau is a scrapper, gets a lot back, attacks now and then with good volleys.