Most Champions are presumably stronger outside the league than they are in it, though some may actually be weaker.
Do you really think they only have four abilities?
What about the levelling up thing?
Overall the effect of being summoned drastically changes their power.
Presumably some champions would actually be powerful enough *COUGHJAXCOUGH* that they could take every other champion in the game at the SAME TIME.
Just not inside one of the fancy little arenas.

Where are people getting all this **** from, anyway?