I'm really disapointed in advice that is a hearsay rather than mathematically evident.
A card has to have a use and this use is to give you tempo. Its its reason, so don't question that.
The second portion people call into question is the cost, 1/3rd life is a large portion and the things you draw need to draw to be worth that. Before you call this best cost situation into question give details as to why it is too little. What are you going to offer that is better than 30 life in a Darkness mark deck? What in a non-darkness mark deck are you going to get thats worth more than 50 life?
It is balanced and fine.