I cant speak for the others, but I'm experienced with Sona.
Sona's W should not be treated as a Heal early on unless you're prepared to do some serious investment into mana to facilitate that. As in, Coin, Faerie charm start, biscuits, and Manaflow band. But as it stands, now starting with a Charm is impossible.
Sona's W is primarily used as a Shield until she starts getting some serious mana regen, as the heal is far too weak for the expensive mana cost, and you will run oom in no time and then are useless.
Moreover, taking Inspiration on Sona means she loses all of the defenses that Resolve gives her, and trust me, as someone that has played both ways for a long time, you FEEL the difference immediately.
Personally I feel like making support items cost 375g would have been good, as it would allow for the remaining gold to be spent on a Charm, two Pots, or a Pot and a Red ward.