No I don't think so. While a wizard can know how to cast more and more spells, it's still limited by the fact he can only cast x number per turn.
I would be ok with it stacking, what is missing in the 4 page rule set though is a little note about that a 1 is always a miss/failure, that would atleast make things not invincible.
There are no natural rolls in AoS unless specifically stated in a special rule. For example, you'll notice it's possible to roll a 7 on a d6, and conceivably a negative number or 0 as well. Another example, casting mystic shield on a unit of liberators makes it impossible to actually roll a 1, so you don't get to re roll your ones because they are now 2s. I saw this other day In a game and the guy trying to re roll his 1s had a really hard time grasping the concept. The spell doesn't make your save a 3 instead of 4, it means you literally add 1 to your save rolls, simple as that.
I wouldn't says he idea of a natural roll mechanic ismissing ie it should be there but they forgot, it's not there because the system is assuming you literally add or subtract from a roll exactly as the rules describe. Again, overthinking it.