Keep in mind that the Duras faction only controlled a certain part of Klingon territory. We know that the Klingons had since broken off relations with the Romulans in favor of a Federation alliance, so it seems possible that the Klingons may have constructed a network of outposts along the Klingon/Romulan border similar to the outposts monitoring the Romulan/Federation Neutral Zone.
Given this, it could be that there were few places where the Romulans could expect to make it into Klingon territory undetected (as I suspect that while starships may not be able to carry sensors sensitive enough to detect cloaked ships, fixed installations dedicated to such a task may be able to... partially supported by the line in Nemesis saying the
Scimitar's cloak was "perfect", which would suggest that the cloaks of other Romulan vessels are not), and of these places, perhaps only one was in Duras-controlled territory. Or perhaps the other places were too near the Federation border and their outposts. Or perhaps going any faster presents an even greater risk of detection by outposts or even starships.
There's also travel time. The Duras sisters were depending on continual Romulan reinforcement in order to keep up the fight... IIRC, they were getting agitated at the first sign of a
delay, let alone the possibility of a missed shipment. Hence the Romulans will try to take the shortest path possible... and there may have been a single shortest point which at some point was narrow enough for the Federation fleet to blockade and prevent the Romulans from effectively bypassing.
Aside from circumstances of Data getting a command
Picard fought for Data to be legally declared a sentient life form with the right to self-determination and the same rights as other Starfleet officers, and now he's going to turn around and discriminate against Data because he's an android? This would be severely inconsistent, and had it been written the other way I assure you someone would have written about "the writers' incompetence in ignoring continuity."
and why Data wasn't canned for disobeying a direct order from his superior in the face of the enemy
Picard explained this himself. If Data had "just followed orders", the operation would have failed. By refusing the order and acting on his initiative, the operation was a success. The ends
can justify the means.