I realize I'm late to the discussion, but having just now reached a point where a toon has a ninth ability, this ridiculous limitation has probably been the end of DA:I for me. Luckily I discovered it before paying for the latest DLC (because, coincidentally, the server was down when I tried to buy it).
This has nothing to do with consoles. I played DA:O and DA2 on XBOX. You could always reach your "not hot buttoned" abilities through the radial menu. This was obviously purposely removed.
So now I am essentially forced to take abilities that I'll never be able to use even if they are situationally useful. For example, my Inquisitor Warrior has no room for for Line in the Sand but it is something I necessarily have to spend a point on just to get to other more generically useful skills. This odd game mechanic (or lack thereof, really) is basically wasting my efforts to advance my character.
I don't understand why the developer would intentionally prevent me from using abilities I've paid for or discourage me from trying to go farther in the game. I certainly have no need for DLC to increase my level now.
Such a ridiculous limitation that has never been necessary in prior DA titles...