Everyone starts somewhere, and of course they can grow in their career. I just didn't see any indication that T'Rul, sent to babysit equipment for the enemy, would return to coordinate military activity at an international level. Besides, just because she's in possession of a relatively high rank doesn't mean that she came by it the way a Starfleet officer would. The Romulans may have a very different military culture than Starfleet. Consider that Sela was very high positioned at the tender age of 23. Did she earn it by climbing the ranks, or was it achieved by political and family connections? How much merit does it take to climb the Romulan military hierarchy compared to simply knowing the right people?
Good questions. I don't know enough of Romulan culture to give you an answer. People I've talked with more familiar with their military would argue that Sela's ascension to commander wasn't realistic. We're later shown officers like N'Vek and Donatra who reach sub-commander and commander at later ages than she did. N'Vek's exact age isn't known, but Donatra was in her early fifties by the time she commanded the Valdore
The Romulan Commander from "Balance of Terror" seemed to be fairly old, having commanded "a hundred campaigns" by the time he faced-off against Kirk and the Enterprise
R. Star wrote:
And would also even make further sense about Sisko's line of "I even recommended him for promotion!" Poor Eddington, probably like Benedict Arnold in that he was already committed to his treason after he got word of getting the promotion that caused him to act that way. Sisko did know about his dreams of wanting to sit in the big chair after all.
The irony is that he finally got to sit in the captain's chair as a leader in the Maquis, only to see his people slaughtered by the Dominion, something Sisko didn't hesitate to throw in his face during an argument: "Michael Eddington gets to take off his gold uniform and play hero. Well, you had your chance. And look where you led them, right into their graves!"
I'm not sure if the writing was meant to tie in with their prior conversations, but it fits perfectly. If the writers took the time match up the dialogue, kudos to them for exemplary attention to detail!