You're right. Why use two IRB's? I was using WA's insert record behavior because I was uploading photos and needed to insert the serverFileName in the DB, which I thought DW's insert record behavior was unable to do. And I was using DW's IRB because it's required to use the Check New Username behavior.
No doubt the solution you outline in your reply would have worked, but while contamplating this issue earlier on, I decided to change my approach to it a bit and now it turns out I won't need to use those two IRB's anymore.
In any case, thank you for your attention.