His card reads that "While this unit is attacking, each of your attacking units gains an objective blast icon." If he's attacking alone or not does that include Vader gaining the icon too??

The key is in the use of text. There are other cards that denote each other card or something to that effect but Vader's ability states each attacking unit.

Therefore, yes, Vader can always benefit from his ability.

Concur. Each unit attacking gets the icon.

And do not confuse "attacking" with "striking". In order for Vader to be "attacking", it would have to be the DS player's turn. If it is the LS player's turn and Vader is participating in the engagement, then he is not attacking; he is defending. Therefore, the ability would not take effect.

And do not confuse "attacking" with "striking". In order for Vader to be "attacking", it would have to be the DS player's turn. If it is the LS player's turn and Vader is participating in the engagement, then he is not attacking; he is defending. Therefore, the ability would not take effect.

True. Not that it really makes a difference in this case as giving your defending units blast damage would do nothing anyways.

And do not confuse "attacking" with "striking". In order for Vader to be "attacking", it would have to be the DS player's turn. If it is the LS player's turn and Vader is participating in the engagement, then he is not attacking; he is defending. Therefore, the ability would not take effect.

True. Not that it really makes a difference in this case as giving your defending units blast damage would do nothing anyways.

With this card, yes. The effect would mean nothing if you could use it as the defender. However, there are many cards where this distinction is key, such as Trooper Assault, Proximity Mine, Smuggling Compartment, and anything with Targeted Strike, such as Luke Skywalker, Han Solo, TIE Attack Squadron, Vader's Lightsaber, Mandalorian Armor, etc., etc.