Boss Fights not Balanced for Party Play

Going thru the campaign with a 2nd player is fine and very fun. The boss fights for party play needs to be re-balanced down a tad. We have yet to beat the chapter 1 boss fight together, but we can beat it no problem when not in a party. This was the case for two separate builds thru act one. The result was the same. Boss took forever in a party, but manageable solo.