Personally, I do feel all of those champions need work to some extent, as their design has not aged perfectly. Lulu I think needs the least work, since she's mostly quite fun and fair now, but she could still use adjustments to her W and E, as they've been causing counterplay issues in lane and have led her to be nerfed into having mana problems and weaker numbers on both of those abilities, to the detriment of her support playstyle.
Soraka I think was reworked with a good idea in mind, but her subsequent balance changes ended up taking her in the wrong direction. At its core, the idea of a dedicated healer to puts themselves at major risk to heal their teammates is a great idea, as forcing interaction between the healer and the enemy team means they don't feel like they're just there to nullify plays. Unfortunately, when Soraka's instant Q self-heal got turned into regen, I feel that interaction was lost, particularly since no balance work was really done to emphasize the health cost to her W (she uses up a lot of mana instead, which defeats the whole purpose of her healing engine). She needs some pretty harsh rebalancing so that she's forced to get up close and personal if she wants to provide good healing to her team, and absolutely needs to lose hard when she gets played as a safe back line healer.
Sona has the same fundamental problem she's had since her release: she does a little bit of everything, and can do it for her entire team, which makes her whole kit feel diluted even when it's strong. Her musical theme is a little underused as well, and she still doesn't feel like she scales up to very high levels of mastery. I'm not entirely sure how she should change in the future, but I feel she could benefit from having slightly fewer, but more concentrated effects.
Janna is, imo, in the best spot here, as I feel only her W needs a rework (it's a pretty boring active). Her Q could use some tweaks so that uncharged tornadoes are weaker, and I'm personally in favor of turning the bonus AD on her ult into something less marksman-synergistic, but otherwise her core design is still pretty great to this day.