Sven is less terrible than he used to be. His most viable form now is as a hard carry with free farm. Get a few mid game damage items(namely armlet, MoM) with a BkB and you should be able to win fights if the enemy is ever stunned. Never play him support.
Here is another coaching session, this one has a different format, a lot more like 'Purge plays a pub'. I had previously talked to Dave for about an hour talking about roaming and ganking strategies. Here is us putting it into action on the euro servers. Enjoy!