Yea you make a point that is a big issue. Something that needs to be completely over hauled is the coster skill ratio.
I could talk all day about action costs of this ability taking up too much space for this ability that I really want to use.
As this is something that I like to see, cause it gets players thinking and rotating there strategies around to meet the core reasoning for there "character build". It's simply something IMO that is not yet finished. So I wouldn't worry too much about that part of the equation just yet.
And yes cure 3 is a major example with "class specific skills" that should only be usable on a particular class.
maybe Cure 1 or cure 2 can be transferable, but with higher Action costs with higher level skills.
You bring up another great topic, is level requirement. Players need to meet the corresponding rank of the skill. R20 skill transferable to only r20 classes, and again only if it is NOT a class specific skill.