Heroic adventures are annoying to solo with the stupid nightfall modifiers, and they're only on Mercury for some dumbass reason. PvP isn't even an option, because of how bad it is. Doing hundreds of strikes is the only other way to get them. This isn't FUN.
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Heroic Strikes will get you two with a faction consumable ghost on for strikes most of the time. Even without it you still have a high chance to get two. Crucible will usually generate one a match, sometimes two with a faction consumable. I personally think heroic strikes are faster, plus more loot but it's definitely not that hard of a grind.