Well then u have never played original DotA then, most veteran/hardcore DotA player i know never play LoL for this reason, and also other reasons such as changed game mechanics and game points benefit. It removes the originality and thrill of DotA from the game, thats why we rejoice as Dota2 came out, and we played dota for almost 8 years.
I'm talking about a new players point of view, and even for a veteran of DotA coming to LoL, he doesn't know the champions so he would have to learn them. And I think the method of changing the default champions every week is a good way to do that. Just my 2 cents.
