Stealth Tactics command card states:

Use while defending to add 1 white die to your defense pool.

When am i able to use this card? Do i have to use this card before rolling the dice and add the white one before rolling? OR can i use the card after seeing what i rolled and try to fix it with the extra white die provided by stealth tactics? It's essentially still 'while defending" is it not?

You have to use it before you roll. You can't add dice to a dice pool after the roll.

The rules reference guide covers all of this under the Attacks section.

Thank you

I don't believe so, but please correct me if I am wrong.

Normally the frame "Use while defending " is AFTER the rerolls of dice. Yes this seems a bit illogical but this is the terminology.

If you had to add it to the pool before rolling wouldn't the wording be "Use while an attacked is declared againts you" ?

"while defending" means, it's up to you. You can roll that additional die anytime in the given time frame.

You can use it before rolling, you can use it after rolling. Using it after rolling just gives you an advantage.

Yes, use while defending allows you to use it any time during the attack. However, adding to your dice pool after the rolls is useless to you. But, any time before the roll is fine. The mild advantage is that the use when declaring things are already known before you have to commit to using it.

daa

"while defending" means, it's up to you. You can roll that additional die anytime in the given time frame.

You can use it before rolling, you can use it after rolling. Using it after rolling just gives you an advantage.

Generally that is right, but not in situations where you add dice. Here is the relevant quote, directly from page 6 of the Rules Reference Guide (emphasis mine):

1. Declare Target: Based upon its attack type ([melee] or [ranged]), the figure performing the attack (referred to as the attacker) declares one eligible target for the attack (referred to as the target).

- For a melee attack, an eligible target is any hostile figure adjacent to the attacker. For a ranged attack, an eligible target is any hostile figure within line of sight of the attacker.

2. Roll Dice: The attacker rolls his attack dice at the same time as the defender rolls defense dice (listed under “Defense” on the target figure’s Hero sheet or Deployment card).

So you have to add dice before step 2, which is rolling dice. You can't roll dice and then add them.