Error(s) born in the mind of Arius engulfed the Church to such an extent that it is valid and not heretical to say that the majority of the Church was Arian
It is not valid, and it is heretical.
Turn on the light-switch, Lighthouse. It would heretical only if one divorces Her from Her human element/attribute, splitting Her in two, where the words the Church make reference only to Her Divine Eternal Truth. As I said prior, when speaking of the Church and error/unorthodoxy/heresy it is referencing Her human element/attribute.
Please provide the source for this "human element" attribute that appears to allow the Church (as you understand it...two elements) to be in error in Faith and morals.
Also, if Arians were heretics, they simply were not Catholics. Surely there was plenty of confusion at that time, but even so, a heretic is severed from the Church
by definition. Don't you understand that?