I think the problem stems from Dancer not really needing this kind of skill. For the Monk, for example, having a way to put your Greased Lightning on pause for a boss's cinematic attacks makes sense because there are now many fights where they can hold on to their GL rather than lose it and need to get it back from scratch, which is a notable DPS loss (not to mention it feels crappy).
For Dancer, we don't really have anything like that. Improvisation's biggest and most frequent benefit is that you can get an extra Saber Dance out of it after a pause in a raid, which is nice, but it's such a small benefit for something that takes up a space on your hot bar. The added healing potency increase is, in the cases of a pause, frankly useless. Healers don't need more healing potency during the most stagnant parts of a fight where the damage is at its most controllable state and with loads of time to rest and let your MP recover. It's the illusion of helping without actually doing anything that improves the experience for your healers.
Being able to pop the buff in the middle of a fight when the team is getting chewed up would be significantly more beneficial, but not at the cost of the Dancer's DPS. The only time where it would be worth the sacrifice is if you'd otherwise wipe as a result. Those kind of wipes only occur when the healers are struggling to stay alive and thus cannot keep up with keeping the team healthy, which are honestly quite rare. Wipes are more commonly caused by not enough people knowing mechanics and you either fail a DPS check, or not enough people are surviving mechanics for it to matter anyway. As long as one healer is staying alive, this problem isn't that prominent, and even when both have been revived, it's still not necessarily wipe material.
It just doesn't feel great to have an action, especially a level 80 capstone action, be designated for such niche circumstances and to be used as fluff between a pause in a raid that doesn't really feel like it's helping you keep your momentum. Dancer just doesn't really have a need for this and it feels superfluous.
What if Improvisation was changed to augment your next Standard Finish or Technical Finish? Here's a random example:
Improvisation - Cooldown is 180 seconds.
Grants the user Improvisation for 20 seconds.
If Standard Step is used, Improvisation is consumed and all enemies hit by Standard Finish will have their damage output decreased by 10% for 8 seconds.
If Technical Step is used, Improvisation is consumed and all allies affected by Technical Finish will receive an 80 Potency HoT for 15 seconds.
This is just an example of what I mean, but you get the point--have Improvisation be an augment of your next dance to provide some kind of utility or survivability aspect. It would be far more usable than the current Improvisation and feel satisfying.