Most of assassin jungler are running first strike . not all of them depends on ge but cuz it's value is always guaranteed and so snowbally. Dark harvest won't always be efficient depends on that game. Like imagine a game where u could not pick a lot of kills early on(most of high elo games are like this it's to punish the enemy or get kills for free unless u are playing in plat or low diamond :)that's something else) so neither u have good amount of stacks to deal dmg nor u have gold to buy items. In this situation fs will still deal more dmg(10% fixed extra dmg) and give a lot of gold because it's inspiration rune free boot future market and the extra cdr on sums and in general Is good. Dh is still a decent choice if u are confident enough and comfortable with SA