I would add that while blood ember boots aren't worthless by any means, the fear effect doesn't last long enough for most situations given that the click takes a considerable amount of time to cast; not bad for lazy duos and trios, but the multitasking required while soloing can be a bit much. On the other hand,
Polished Obsidian Great Axe offers a more substantial fear at level 40, 9 levels before SKs can even mem the spell. Though that does mean relying on rng/dex, it's still a great option if already using a two-hander–just swap in and out as needed. The duration of invoke fear is significant and, more often than not, another proc will occur before the previous one wears off.