Death Prophet is a very strong mid hero because of her good attack animation, good range, and extremely spammable low mana nuke. She's pretty good against heroes like Ember spirit, unless you let him get close to you.
Try to be a bit more precise with your item build that I was this game. I regret not going Arcane Boots into Shivas or Sheep. It would have been a lot stronger than spending 5k gold on the Mek and Euls Scepter. I also could have played wayyyy better in the late game.
Try to buy tanky items and go around casting crypt swarms and silence to slow down your opponents from doing major damage and you should be able to eventually dps them down.