Well of course it has a lot more uses, but that's the main thing that suffers if the cooldown rises. For example, when leaving after having used it offensively.
I don't understand why people say Bard's heal is bad, especially when they take it last. It's stronger than Sona or Nami's individual heal, and can be set down as a precaution in case the enemy team comes or if your allies or you take harass. It also gives you something to leave for allies whenever you roam, whether or whether not you want to make things happen with their lane opponent.
For comparison:
Sona: MINIMUM HEAL: 30 / 50 / 70 / 90 / 110 (+ 20% AP) MAXIMUM HEAL: 45 / 75 / 105 / 135 / 165 (+ 30% AP) 」
Nami: HEAL: 65 / 95 / 125 / 155 / 185 (+ 30% AP)
Bard: MINIMUM HEAL: 30 / 60 / 90 / 120 / 150 (+ 30% AP) MAXIMUM HEAL: 70 / 110 / 150 / 190 / 230 (+ 60% AP)
Granted Nami's heal can also bounce and is usually maxed first, but Sona's heal never reaches maximum potential, and the shield is pretty impractical as well. Whatever. Point is I prefer taking W second and recommend it to others as well. Then again, I also build AP with Bard so...
Either way, that still means it takes ten or twelve levels until it becomes a buff. I mean, I don't think it will improve Bard, but the cooldown changes are so insignificant I don't think it'd really matter at all.
Thinking about it, even if chimes reduced the cooldown by 2 seconds and the cooldown was 19 / 18 / 17 / 16 / 15 instead of 18 / 17 / 16 / 15 / 14, I'd be hesitant to call it a straight buff so much as just a change.