I'll be honest, while I agree there is a level inflation issue at novice levels, I do think that the difficulty of leveling scales remarkably for non-pilot classes. The achievements are simply harder to do. As a pilot, at least half of the achieves technically have 4 people working on them, and another chunk such as use any given tool can be EASILY ground during downtime on a point or between kills if you have a half-decent engineer to keep up with the DPS to your parts.
Pilot is truly the easiest class to level IMO, and yet it is the hardest class to play as a good pilot needs to manage his crew well, something I still have trouble with from time to time. Meanwhile I'm finding engineer achieves incredibly hard to get because they require such specific actions. (You try asking a captain to let his baloon break so you can rebuild it or explain why you arent fixing the goldfish hull cause you need 19 more rebuilds on it) Yeah, no captain is gonna like that. How about those combat ones? Gunnery achieves arent quite as bad.
As for XP for kills, that wont work. I cannot tell you how many times I've had my ship all but finish an enemy only to have an ally gat that last sliver of health and get the kill credit. In regards to levels, you have to realize that people like the numbers, it makes them feel accomplished. by the time they get to high levels they are more likely to stick around but those first few levels are key to making people feel accomplished.
finally, if this rinntaq guy is as good as you say he is max, I need to borrow him. I've had the get 5 and get 20 kills at 1kM achives sitting undone for a while now, both still at 0. HOw you get a kill at that range is truly beyond me.