I think it puts a MUCH greater premium on the most vanilla high damage-output powers, and then even more so on anything that 'front loads' damage output, such as minor action attacks, reactions, and interrupts. Certain classes, like rangers obviously, will REALLY benefit from this. Other classes, like most controllers, will find their shtick has been significantly devalued, 2 rounds simply isn't enough time for most control to really be leveraged effectively (though at least a few of the more ephemeral UEONT effects may be a little bit more worthwhile).
Yes it would - if you recover all you HP and encounter powers without a cost after a short rest. However, if we make this associated with a cost for these recoveries, you would like to save you high damage output powers. This means that for a low threat encounter that last for two rounds (like in 5th edition), you might only want to use your at-wills and maybe one encounter power. As the damage output decreases, this lower threat actually becomes harder to handle, allowing me as a DM to place small logical skirmishes in my adventure design (without creating a 1+ hour fight). Some sentries, a street thug, etc. which might fit into the overall story, but is maybe not the "grand battle", the party is saving their resources for.