I like Bashir, I really do. He was one of the few characters in the novels I felt had a true understanding of just how horrible this universe can be, and yet he still didn't give up. But yes, I also feel he should remain comatose. Like hbquickcomjamesl said, it trivializes everything. And Star Trek has a bad trackrecord with that. EIther the hero survives the sacrifice play ALL THE TIME, or they die. But give it a good few months, sometimes a year or two, and hey presto, they're back. Data and Janeway being some good examples of that. Spock ofcourse. And if it isn't about sacrifice. Characters who commit crimes, have done bad things. Even if it was for the sake of the greater good. It's a small tap on the wrist. 'You won't ever make admiral now Picard'. The guy already didn't want to be.
No, I think it would make sense that Julian doesn't come back.
True...but...two things.
Firstly, fiction doesn't necessarily have to be 'realistic' or in this case, if it dies, it has to be realistic in terms of Trek. As you have said..in Trek, people come back. It's part of it.
Secondly, with Bashir gone, the number of Deep Space Nine characters actually anywhere remotely near Deep Space Nine is again reduced. I think we are down to what...three on the station now? One of whom was supporting cast (Nog). This entire book (which was, as I have said, very very good.) features only three characters from the show. One supporting cast, one guest cast, and one main...who is in a coma. This ain't to say I want less books like this, far from it, it's an excellent book, and the Trek Lit can go off and focus on these characters more than the series did. But as an overall picture, Ds9 is shattered and split all over the place. Bashir is a big character, and if his arc ends here, too much is let unsatisfactory. For a start, I do t remember the last time he interacted with his best friend O'Brien, and I think his relationship with Ezri was handled badly way back when.
Maybe it's time to get those familiar voices around him, as well as Garak.
None of which is a criticism on this book, Una has made the Cardassian Union a much richer tapestry over the years.