I've been spread trading ER2 against other CME index futures for a little more than 1 year now, and I think increase now is quite right on this purpose.
After an incredible money making period during late july-early august, it seems that price discrepancies have increased and ER2 behaviour is now totally different from what it was previously( and I'm suffering a DD on this system... not so bad but releasing part of the year profits ).
There was a day in august when I lost 900 $ per contract in 20 minutes... ER2 was just going north while the other instrument barely moved... This never happened in my experience. It seems that something has changed in the inter index arb algos or the number of guys doing it... But it's not the CME/ICE change since the russell stock index remains the same.