Given the poor performance of the explorer ships in a ramming role, is there going to be some re-thinking about their usage?
Could they be re-fitted as point defence platforms to protect the larger ships or given faster engines to increase their hit chance?
They can't protect any other units with point defense until the Russians develop datalinked point defense, which is a ways away at this point. Additionally, they have run out of explorer class craft for now. It was a good lesson, though. The explorers would have performed better as rammers if they had military engines, as they would have at least been faster than their prey. The ramming thing was only ever an emergency stopgap, though. The original plan was to us them as rammers at the warp point to stop the D'Bringi if they tried to enter the Solar System, and in that situation, supported by the asteroid forts and laser buoys, and the remnants of the fleet, they might have done okay. If enough time passed, the USSR planned to refit them to mount plasma guns, which are the only weapon small enough to fit on an explorer class hull. Unfortunately, the Pg's aren't developed yet, and Marshal Kosygin decided to waste them on a desperate attack to which they weren't suited. Although they did do well as a distraction that kept the D'Bringi beam cruisers away from the Russian missile ships, at least for a short time.
Also the soviet destroyers got hammered, is that because they were so badly out-matched or is it just how things go with beam engagements?
A bit of both. The destroyers had green crews, as they had just been launched a month or two before, and that didn't help. They were outclassed by the D'Bringi beam cruisers, which were bigger, better armed and armored, and mostly had crack crews at this point. And finally, Marshal Kosygin sacrificed them to ensure his cruisers got back. Some, of the DD's might have got out if the Marshal had ordered them to retreat at the same time he ordered his cruisers to return to the solar system, but if he did that, and the D'Bringi fleet wasn't under pressure from the DD's, they might have concentrated their fire on the retreating Russian cruisers.