[{quoted}](name=The Yetii Rider,realm=NA,application-id=3ErqAdtq,discussion-id=nmk7yQLE,comment-id=00020000000000000000,timestamp=2016-07-03T19:39:46.972+0000)
Sona's W is being completely changed. You can't say "It's used for the shield late-game" when they're reworking her.
New heal has higher bases. New heal has a shorter cooldown. There are now items that increase healing done, and you can stack them. Sona's shield no longer extends its duration by tagging multiple allies. Sona's E now gives out of combat move speed so it's harder to stack up her shield in battle where it counts. It's a completely different ability.
It's not a major overhaul. W is also losing its % missing health scaling, and the aoe shield can tag up to 5 targets while the heal is only Sona and one other person. That isn't changing, and thus the core reasoning behind using her W (the shield) still stands. Both before and after the upcoming patch, Sona's shield will be the point of W, not the heal.
With this said, the point of increasing Sona's healing done is because the same items synergize with other parts of her kit. Athene's stacks while you use your Q, which you'll use often, and then it effectively doubles your heal on W. Athene's and Crucible beefs up your shield while it beefs up your heal, which is more important as it's more effective health passed around more people.
Edit: Oh wait, this was over Lich, not Locket.
Thus, what's the point of a cleanse and 15 more heal/shield per 100 healed/shielded when you can get a few hundred more damage on a target, full stack your Athene's, and pass that bonus healing to your ally on a very decreased cooldown, thus implying this can happen over and over? Assuming we don't need the cleanse from Crucible.