the cost becomes irrelevant once you start playing two characters, you will be having too much fun to notice :P

as for the healer question... most players using RAF take about 2 days /played to level a set of toons to 60 (without rushing or boosting - levels fly by, you can even miss out zones /quests you hated), so in the 90 days RAF time you can quite easily get at least two of each class up to 60, and then start mix and matching combinations to find the best pair that matches your play style