I really like Dancing Strikes for Bladedancer but it seems very underwhelming compared to every other option as a support skill or a main damage skill. Gladiators Oath being a unique for it that is also fairly underwhelming (mainly due to its item base) and doesn’t really help make Dancing Strikes better.
My suggestions to help would be to either allow some way for Dancing Strikes to become 0 mana cost, or to create a way for it to guarantee a proc of Shadow Cascade.
You could replace the create a fighting arena affix on Gladiators Oath to make it guarantee a Shadow Cascade proc on the 4th attack. Since the sword also gives bonus melee attack speed this synergizes with the Leveraged Momentum node for Shadow Cascade already, and making it only proc off the 4th attack means the Hidden Blade node for Dancing Strikes is still somewhat viable to just have a chance at more procs on attacks 1-3.
As for making Dancing Strikes 0 mana cost I’m unsure of how to do this the best way, but it could be implemented with a 1 or 3 point node in the skills tree to reduce mana cost to 0, or instead of replacing the arena affix on Gladiators Oath with the Shadow Cascade proc, could instead do an affix that states “Dancing Strikes now costs 0 mana”.
The main benefit of the 0 mana cost would be to run Sapping Strikes and Coated Blades in the passive tree, allowing the skill to more properly fill a support role. Create the arena for damage done/taken benefits, to boost something like Lethal Mirage even more. Losing out on Coated Blades makes it currently not worth taking for that kind of situation in my opinion.