Although I agree that Death Prophet (DP) is not a squishy hero,
I personally feel like DP is hard for new players to use because she is very easy to kill early on in the game (squishy).
Personally I would recommend Tidehunter, as he possesses good survivability as a result of his skills Anchor Smash and Kraken Shell.
As Tidehunter, you would want to level your skills as follows (the number refers to which skill should be upped each subsequent level, from left to right): 3, 2, 3, 1, 3, 4, 3, 2, 2
My suggested skill progression will provide you with enough damage to burst your opponent using Anchor Smash, while also providing survivability. Anchor Smash will reduce the attack damage of enemy heroes and, combined with kraken shell, means you might take low or no damage at all.
Feel free to replace Gush with another point of Kraken Shell for extra safety. I did not include this in my suggestion because sometimes you'll need tools to chase your enemy when your team comes to bank.
For the item build, if you are facing high damage per second (dps) heroes, one item that you should definitely pick up is Vanguard (I know the damage block won't stack with your Kraken Shell, but Vanguard will provide you with a good amount of health and regeneration).
If you are facing an enemy with magical burst, buy Cloak and a Vitality Booster to increase your hp.