Yes. In WoW it works like this 5 points > 10 > 15 > 20 > 25 > 30. The points don't have to be spent on that exact tier but they must be spent cumulative throughout the previous tiers before moving on (with the exception of the first obviously).
Yeah I'm aware of it, but what about the rest of my post? Why like this instead of like that? As long as pre-rank 30 skills (that aren't spec-based) are kept cross-classable while everything else is class-specific, it should replace the need for "tiers".