One thing I recall from the old Flock book was that those ones baptized with sincere doubts should be shown mercy and assisted where possible. On the other hand, when it came to someone who decided to join a church the language was more harsh. It was something like, "they're already under judgement."
As far as most JWs feel, I don't think there's anyway to gauge that because there's no way a JW will ever be honest regarding this subject. Me personally, if a person joined a church, to me at least it would appear they followed their heart and considering we're not to judge anyone, that's between them and God and I shouldn't condemn them. When it comes to Agnostics, I feel they're the only honest people left on this planet.