Technically neither, your Seeker of the Way deals damage after he dies and since his last known information included him having lifelink you gain life from him dealing damage. I'm not trying to be pedantic but your Seeker dies as a SBA and then the trigger goes on the stack and uses last known information to deal the damage. This matters if the same spell killed other creatures since they will not be dealt damage by the seeker because of the Arcbond trigger.
February 28, 2015 9:19 a.m.
The delayed triggered ability Arcbond creates will trigger even if the target creature is dealt lethal damage. For example, if a 3/3 creature is targeted by Arcbond and later in the turn it blocks a 7/7 creature, the 3/3 creature will deal 7 damage each other creature and each player
Per gatherer. So yeah, lifelink would still be applied because he's doing the damage even though he's taken leathal damage.