Anne is definitively Soler--I'm 99.99% sure of it. Listen to the scene when she speaks with Richellieu--it's basically Huntik's Sophie Casterwill sans accent.
As for the other teen musketeers, the blond one is voiced by Rachel Lillis-- that's the only one I'm sure about.
Were this something like One Piece, where you have tons of characters appearing regularly, I'd be right there with you. However, this, like Pokemon, is a different kettle of fish, with a metric ton of one-shot characters and the like. Given the relatively limited pool of NY actors (particularly for female roles) I think reusing actors will eventually be a given--at least, unless you go by the theory that those sort of minor roles are precisely the sort that should be given to unknown actors, therefore increasing the size of the VA pool. That said, I do think that reusing Michael Pollock this soon after the Japan arc is too much, even if he is well-cast in the role.
Soler voices Sheer? First I'd heard of it. I get that she's rather versatile, but I'd probably never have pegged her as that particular character--mostly I've just been assuming that her VA is a new one. Is there any evidence for this, or is this your conclusion based on her past work?
[NY VA Geekery]As for Mansley, he's been around, although mostly in TMNT, which was the first show to use him and where he played about 5 different prominent characters. He's also done some work for a few dubs (he was King Nebra/Cobra in One Piece), although he's not exactly a mainstay--right now I'd put him alongside someone like Michael Alston Bailey when it comes to prominence. [/NY VA geekery]