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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Yeah, those modifiers making either void, arc or solar effective make it very tough to do solo. Almost no way you're finishing it without running out of time.