Daggers, Crit, and Spectral Throw

Hey I'm decently new to the game (dabbled during beta).

I love ST, and I have this idea for a crit dagger spec. With a lot of crit.

http://www.pathofexile.com/passive-skill-tree/AAAAAgABAAYDlgV9DkgRlhHVFfYYTRmKGlUbyBzcLOEtgzJ-NJM26DpSOyhDMUZxSshOKlbqV5dYr1pSW69eE2BBYENhIWJ5Y3Bko2eAbj1uqm-ecFJwVnDVeA14SX5Zf8aDCYN8hO-IQo1-joqQG5MnlwaaE5tdm4ObtaEiokCoB6iaqW6sZrQMtfK2Qbe2vqfAUcHFwzrEospKzZjQ7th229TjhOn-7-Pyl_Pq9Pj3ow==


What do you guys think? I'm unsure if I will have enough strength to make Iron Grip worthwhile.

There are no life nodes, wont survive post lvl 15.