The Survivor feat reads as follows:
Prerequisite: Con 13, Diehard, Endurance.
Benefit: You gain a +5 bonus on all Constitution checks made to stabilize while dying. Once per day, if you are struck by a critical hit or sneak attack, you can spend an immediate action to negate the critical or the sneak attack damage, making the attack a normal hit.
Survivor has Diehard as a prerequisite, which says:
Benefit: When your hit point total is below 0, but you are not dead, you automatically stabilize. You do not need to make a Constitution check each round to avoid losing additional hit points. You may choose to act as if you were disabled, rather than dying. You must make this decision as soon as you are reduced to negative hit points (even if it isn’t your turn). If you do not choose to act as if you were disabled, you immediately fall unconscious.
When using this feat, you are staggered. You can take a move action without further injuring yourself, but if you perform any standard action (or any other action deemed as strenuous, including some swift actions, such as casting a quickened spell) you take 1 point of damage after completing the act. If your negative hit points are equal to or greater than your Constitution score, you immediately die.
Normal: A character without this feat who is reduced to negative hit points is unconscious and dying.
Emphasis mine. Does the fact that Diehard causes you to automatically stabilize render the first part of Survivor completely useless? Are there any circumstances where you would make a Constitution check to stabilize while dying where Diehard would not apply?