I cannot make any progress on my Warlock's Masterwork objective for the Solstice of Heroes bond. I've defeated Calus in the Prestige Raid, beaten multiple Heroic Strikes, run the Nightfall on Regular and Prestige above the threshold, killed a Lost Sector boss, killed VIP Minotaurs in the Vex Rings mini-event and none of them have granted any progress towards the "Defeat Bosses" objective. I am permanently stuck at 8/10.
EDIT: For those who might be in a similar situation: The bond does not progress by defeating Raid bosses, Nightfall bosses, Strikes bosses or Lost Sector bosses but DOES progress by defeating Public Event bosses.
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Try heroic public events