When I hear people calling "it's undefeated, let's ban them", I think they simply don' like new things.
Cantabrian circle is something great - but only in good players hands. You have to know how to use circle - of course you can just press f and put on objective, but trust me guys - you will be massacred.
On the other hand circle help us ballance game. In my opinion it's ridiculus when axe nation got missiles advantage over steppe nation.Figthing against opponent who use circle is very simple- if you hate circle and don't want combination of light cav and long range archers - BUY SASSANIDS CLIBINARII.
This unit is ha murder - no horse archer unit can hold it (of course if well used).