Rucker would be a 10, yes. If he was not a restricted player and had stayed with his original club the entire time, he'd be capped. If you're at the one club for longer than 5 years, you get a point discounted while you stay there. Longer than 10 years, and it's a 3 point discount. If you give 10 years service to a single club, you can transfer your rating to another club (e.g., Bradtke being a 7 internally at Brisbane, I think).
Adelaide is in quite a good position as long as Maher, Holmes and Forman stay - their external rating is 27, but their internal rating is just 15.
To the person who asked about the points cap - there is a dual cap system in place: salary cap and points cap. Salary cap should be a familiar concept to you. The points cap attempts to combat things like an Andrew Gaze agreeing to play cheap for the Tigers, etc. Each club is permitted x points (it was 66 in 04/05 but I think it might've been increased for 05/06 - not sure) to allocate to its ten rostered players. Imports and top-level locals are nearly always rated a 10. Rookies are 1, college grads are often a 3 in their first year, a player like Mark Nash is a 7 for 06/07. The point values were previously handled by a vote of all club coaches I think, but this coming season it's been done statistically.
Once the values have been released, players can appeal them if they disagree. Also, if a player does not have a contract late in the off-season, they can appeal on the grounds that the points system is precluding them from gaining employment and potentially get a reduction.