In an earlier post, I described some testing I did with Clinging Shadows. Bottom line, it bugs out Leaping Shot's new upgrade and regular Flank Attack. Instead of going to full duration stealth after those skills complete, you only get the additional 3 secs of Clinging Shadows.
But don't take my word for it, test it yourself.. Having some additional verification would be helpful.
The way Clinging Shadows works is it keeps you stealthed for 3 more seconds after you start attacking. Now there are two things to know about stealth:
1. Stealth doesn't overwrite itself - that means you have to wait the end of the 3s before trying to hide again.
2. When you're using the Stealth ability the cooldown starts only when you're out of stealth - that means you can't reduce its cooldown during these 3s. However if you're stealthed using Leaping Shot/Flank Attack the cooldown of the Stealth ability will be reduced (by your attacks) or refreshed (by I Was Never Here) like it should.
Clinging Shadows works especially well vs bosses because I Was Never Here can't help you, however you have to use Leaping Shot/Flank Attack when you're out of stealth. Also you should use your multi hiting abilities (Hidden/Throwing/Spinning Blades) after Leaping Shot/Flank Attack in order to reduce the cooldown of Stealth and be able to hide again.
More tests about the timings of different attacks are required but vs bosses it should be something like that:
Archers - Mark of the Rift, Mark of Death, Shadow Strike, Leaping Shot, Hidden Blades, Throwing Blades, Long Shot, Stealth, Mark of Death
Dual Daggers - Mark of the Rift, Mark of Death, Shadow Strike, Flank Attack, Hidden Blades, Throwing Blades, Spinning Blades, Stealth, Mark of Death
VS regulars enemies you can replace Mark of the Rift/Death with Full Draw/Explosive Shot or Twin Fangs/Deathblow to have more attacks to cycle through