I wish they would do what they said they would and add Romulan and Omega Marks to Romulan/Borg story missions.
A meaningful amount as well. Spending ages on New Romulus just to get 10 Marks is silly. Missions should be awarding 30+ minimum. Featured episodes and story missions 50 and so on...
The better source of marks are the patrols and Red Alert in Tau Dewa. if you want to earn unlimited marks on the ground fast you have to scan radiation samples. if you are good at the minigame you can get up to 30 marks for scanning 10-15 samples
I'm afraid that I don't have shortage of Omega Marks. At least not yet. When I start producing equipment it might a different, but I doubt it. Dilithium will the limiting factor then.
If you want Romulan Marks, team up with other people.
Doing the Ground missions, with a team of 5, you only need to collect a 5th of what you would have to collect by yourself.
Doing the Daily Patrol, sure you get more enemy, but they will die a lot faster if you are in a group. And you will probably have chance at better (trash) loot.
Just avoid the Tholian mission at Beta Thoridor or Beta Lankal. The one where you have to beam up artifacts flowing in space. Its bugged. You will get the number of enemies for your team size, but you will all be in your own individual instances. Fightling off 5 times the correct number of Tholians is not fun.
And if all else failed, just spam "Acamer" 5 or 6 times and you've got 60 marks in minutes. Boring but quick.