I've been a Duke for a while, and just earned my Rear Admiral-ship.
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Ranking SUX. Pure and simple. I don't know how I got to Duke in the Empire. I was trying to grind ranks in Fed space, and every time I hit the Empire to cash bounties, there was another promotion mission. This was pre 2.1, so I can see that maybe I was choosing empire factions to run missions for. They didn't have the little advancement bar back then, so I can't comment.
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Feds ranking.. OMG. Awful. My numbers showed it was 4 delivery missions per 1% on the last promotion, and it took me a week to grind the last 400 missions on Tun. I had to mode switch to stack the max 20 mission count, and I picked up new missions for other stops on my 'route' while I was running it. Between that and donation missions, I got about 7-10% per 'run'. It was pretty much break-even credits wise, spending what I made doing the runs on donations. Still, over a week, hard core, nothing but grinding for 3-4 hours a night. It was not fun. There has to be a better way. If 17 Draconis was still working, I would have gladly spent the 100 million to do the last promotion. The only reason i did it was the rumor the Thargoids would be here soon and I didn't want to run delivery missions under an alien threat, and I was already an Ensign.
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I don't believe in the everything now philosophy. I've worked hard for the ranks I have, and the credits to afford the rank locked ships. But the ranking system needs to be fixed. Delivery missions as requirements for promotion opportunities seems... silly. Delivering 2 million tons of fish/water/Consumer Electronics, and ba-zillions of gigabytes of data doesn't seem ( to me at least ) to be Admiral making material. I would think I'd get a LOT more rep if I was running search and destroy missions for Hudson/Winters. Or even delivering war materials for them. Combat bonds should be perfect for this, or killing pirate lords, or strikes on Empire systems. Something more meaningful than delivery boy. Maybe missions specific to naval progression, that would give 3-5%..