all enchatment removal is more less uncounterable, but i agree that crumble is quite strong.
Nevertheless, the risk of it not working is present when you select the spell. If you don't have ini, the mage can move away and you don't use it. Right now you always have to work around potential nullifies, this really makes equipment removal faster sometime, but if you want to remove armor for example your mage has to act first before the creatures benefiting of reduced armor....
I am still of the opinion that the 2mana reduction wouldn't need to be necessary.
Otherhand armor ward might see more play, less of this "nullify" saves my armor wizard always has his metamagic tricks might be reduced.
And consider academy: The full action is really valueable there, so ok while the equipment can be casted with the "cheaper" qc.