So, most of this is just based on personal experience, and more about the context these Attributes operate in than the math behind them.
Starting around Level 5, the game becomes more aggressive with its Rolls. This is not just because of how Attribute Rolls increase by ~2 where Defenses only increase by 1, but also because character builds truly come together and more Feat Points are available for more Advantage, which as GM mentioned has a bigger impact the more dice you have.
As a result, the higher you go in Levels, the more of a rocket-tag game it becomes, with the first hit often determining the outcome or at least giving a big advantage. This is a little bit less true for simple build NPCs who don’t have to spend Attribute Points to get up to 30+ in Defense Scores, but their Attacks work against Player Characters just the same as the other way around.
This contributes to Defend Interrupt builds being popular. They have the Advantage of using the exact same scaling as Attack Rolls instead of a static value. In addition, Defense Scores get more and more expensive to increase at the cost of Attack and utility potential.
Regarding Boon Invocations, the Rolls look alright for their respective Power Levels. Here too however, higher Rolls are not only easier to achieve with easy-to-get Advantage, lower Rolls will usually still have very positive results. You do not need to Roll a 26 using your Creation 8 for the Heal Boon to work, with an easily achievable 21 even without Advantage you will still be Healing 2d6 HP, the maximum possible for a Level 1 character.
Now, this is expected to happen to some degree. Being better at things the more powerful you get is a rewarding experience for players, and in most cases the players are on the same side. It’s not a PvP game, though even that works to a limited extent.
However, solely based on personal experience, I would say it goes a bit too far. A Roll is measured by its environment, on the Challenge Ratings and Defense Scores it meets, which (with the default balancing suggestions provided by the rules and the context of Advantage) makes higher Attributes a bit too powerful in my opinion.
So far I’m a fan of @TrinitysEnd’s Equipment Overhaul homebrew, which both expands equipment options particularly of the defensive type and raises Defenses at higher Levels with less need for expensive Attribute or Feat Point investments. It’s not for everyone however, since it adds some complexity to a game that tries to remain simplistic for many things.
In conclusion, I think if anything, the dice of the high Attributes are actually a little too oppressive. Yes, the averages look alright for things like Boon Invocations, but that ignores the context that characters with access to these Attributes usually have a very easy time boosting their results using Advantage and (very often) Extraordinary Items.
Attribute 10 especially is certainly not in need of a boost, when even with Disadvantage it fairly regularly clears any Challenge Rating it would realistically encounter.