Indeed Sona's passive is much harder to use in its current iteration in complete contrast to before Fearless' nerfs to her. **Firstly, **all of her cooldowns are longer, so you gain stacks more slowly and get Power Chords less frequently, by about 43% less often. **Secondly, **her cooldowns are now differentiated ruining one of Sona's trademark features of having them being identical, a step away from Sona's identity making her no longer feel like herself. Due to her abilities' cooldowns being different from each other, it becomes difficult to cast the exact one you want. Do you waste it on Staccato which had its damage blatantly nerfed by an unadulterated 25%? Do you wait 25% seconds longer for Aria to pop up while that assassin blows up your ADC so that MAYBE it'll be enough to save somebody else? Or do you wait an entire 50% seconds longer and hold out on this tool completely the entire teamfight, all the while desperately praying that your team wins this 4v5 so you can pin down a straggler with your slow?
Whilst the only direct nerf to Power Chord was the unjustified damage reduction to Staccato, both the passive as whole as well as Dimuendo/Tempo individually were indirectly nerfed severely by Sona's dual CD nerfs. The longer cooldowns as well as the identity-ruining cooldown-differentiation.