There have been a couple of times where I've had a Blade Historian in play, but found that my attacking creatures weren't double striking. I thought it may have been me misreading the board or just missing something, but in my last game it was readily apparent as I swung for what would have been lethal due to double strike and my opponent single blocked, but the second strike never came. I'm not even sure it got first strike, so the ability didn't seem to be active at all. The problem is inconsistent, as there have been times it worked. I think it might have only activated while Blade Historian was also attacking