He is stronger than he was before, the small changes they gave to him did not weaken him one bit. He is a huge lane bully and will win nearly every fight as long as there are minions around to get his passive shield built up, but apart from lane it is hard to use him well for more game presence. He is still fairly slow, though his new W does make him speed up in team fights, but without much cc you have to be really good at knowing where the other team is going to be. Always max his e.

I always built him as an AP bruiser/tank mage, so my builds for him haven't changed at all. I don't really think ludens echo is good on him, but I have heard good arguments for it (shield damage stacks it)

With Items always start Will of the Ancients, only viable first item that I have found. I nearly always start boots and pots first buy of the game I like the speed for early lane dominance, but amp tome, cloth armor, and dorans shield are all good starters depending on your lane match up and how aggressive you play. Doran's ring I find to be week, don't start it.

Just play aggressive in lane, and know how and when to use your ability's on minions to win trades. Morde naturally pushed lane to win trades, so I find him best fit for top lane right now, and having tele helps with your late game immobility and actually gives you some affect on map wide positioning.

In fights try not to over fill your shield, often times your e will fill it completely late game, wait a split second before using you q and you will get more effectiveness out of both abilities. Morde's ult is one of the strongest swinging abilities in the game if you have some spell vamp - and depending on the matchup it can be used to force their tanks out of the fight or delete the enemy carry, find out who you want to use it on, and always use it on them, your ult (generally) is best used for AD marksman, but can be used for anyone half health or less that you want to stop in their tracks. And don't forget to macro your ult after killing someone with it, it gives you passive shield, more spell vamp, more damage, and sometimes they start to focus it over you, which is good.