Tiered traits might not be the best solution, but it is a good solution. Talent traits don't feel meaningful when you can access all traits at 10 points, and there's a clear imbalance between trait's potency. Yes, they could iterate on the traits and come up with 12 (15) equally powerful traits, but equally powerful doesn't mean equally useful, and you'd still likely end up with most builds being 30/10/10/10/10.
Tiered traits do 2 things. First, it makes every trait choice meaningful, and it means you might have tradeoffs to get certain traits you want.
Second, it makes it so that your third trait choice in a line isn't the least meaningful choice. When you can get every trait at 10, then you will choose the definitive trait, rather than having it be something you get because you chose to specialize in a line.
With tiered traits, the ideal way to place them would be to have more generic traits in the first tier, somewhat specialized traits in the second tier, and line-defining traits in the second tier. Whether they did that, I don't know, but there's still time for iteration on this.