Re: is there a correct learning path?
Common principles can be found in most techniques, what you learn from techniques that you 'dont need' can be applied to techniques that you do need.
Also in a class of many grades then all grades must be catered for, it would be a shame to split the class up constantly and only get people to do things that they need for their gradings making them only able to train with people of their own grade.
Half the fun of aikido for me, is that everyone gets to train with everyone, its a shame to split that up.
It also depends on what you percieve as what you 'need', if you stop being in a hurry to get the next belt then you can just enjoy your training and let the belt come when, as Bronson said, you know everything on the grading
are there no specialised courses or things like that aimed specifically at your level?