Since it would be required to save those several points for every boss or instance, it seems like a lot of data that needs to be carried around by every player which raises the traffic significantly.

What I don't understand about your explanation is why there would need to be points between 1 and 10 when it's only relevant if you have 10 or not at any given mechanic. You say people with 8 points can't joyn someone with 10. But what's the matter if they have 8 points or just 1. And how is it determined if you get 1 or 8 points?