Sona does not like HsP early!
AP/AH early>HsP early. Diadem, Moonstone ARE BAD OPENERS. Staff of flowing water is secretly the best opener EVEN when there is no AP on team because there is no cheaper access to 70 AP 25 AH and those are the stats you need early.
For free Sona LP go Staff > Archangels for max AP/AH early then pivot into HsP. My preference is moonstone into Dawncore.
HsP is a multiplier. If you multiply a small number you get a small number. AKA Slapping X% HsP on Sona low base W (90 hp heals) does not net you anything. You first have to invest in AP.