If Bashir has no friends, he should have joined the Aventine, another ship or went back and got a job at Starfleet Medical.
Considering the state of the relationship between Dax and Bashir, transferring to Aventine
was likely not a great option (also remember she had her pick of personnel after taking command and she chose Tarses as her CMO).
I know. *sigh* Look, whether the DS9 relaunch picks up where it left off or not--the sooner SOMEONE reconciles the two after the events of ZSG...the better