I think the recurve bow should be replaced with a mini Runaan's so the build path is smoother as right now you get literally no benefits until you finish Runaan's. Actually I lie because you still need some AD to make the other shots do damage, maybe the base damage should be increased.
In general Runaan's is conceptionally fine it just needs some tweaks and buffs as the extra bolts do 0 damage compared to the explosive damage crit gives and the radius for the bolts is still too small. Lowering crit damage would also naturally make Runaan's more enticing as an alternate build but would still need other tweaks.
Here's an idea.
Mini Runaan's: Builds from Long Sword, Dagger + 310g (total 1220g)
Stats: 25% AS, UNIQUE PASSIVE: Your basic attacks fire minor bolts at 2 nearby targets, each dealing 10 (+ 25% AD) physical damage and applying on-hit effects. Bolts have 400 range.
Runaan's Hurricane: Builds from Mini Runaan's + Dagger + Dagger + 180g (total 2300g)
Stats: 70% AS, UNIQUE PASSIVE: Your basic attacks fire major bolts at 2 nearby targets, each dealing 30 (+ 50% AD) physical damage and applying on-hit effects. Bolts have 400 range.
There are flaws but I think the direction is good. The big question atm is AD from Long Sword disappearing because the base damage for the bolts does not apply on your base attack. Maybe that base damage could be turned into a second Unique Passive so basic AA's and the bolts get the benefit. An alternative for Mini Runaan's is to keep the %AD at 50% but have only 1 bolt until you upgrade.