...So how important is it really for you to see an active rep in an ANN thread?
Very important. I don't believe any service to be perfect that won't ever any troubles so a quality customer service is must, although you mention only ann but for me support works in any form (ann support/live chat/email/phone).
On the other hand, some people might not care as long as the casino works and pays.
I care. Even if casino may be working properly, but it there is no proper support, I feel this lingering doubt about casino's legitimacy.