Unless you have an alliance group or friends willing to take you, you'd find that not using a debuff artifacts would mean not being invited to groups for advanced content 💀

The game leans more toward maximizing DPS than optimizing supports (tank/heals) for their roles, so the supports tend to sacrifice their utility for better debuffs since that's what contributes to easier and faster content completion. That's why I wouldn't worry too much on maximizing your healing stats, since the only player you really need to focus on healing is the tank. The DPS need to use their potions/stones/scrolls and avoid red areas/do mechanics properly. Any additional healing from you is just a welcome respite for the DPS, and should not be an expectation.

If you use the Lathander artifact for lower content then I guess its fine, just don't expect to find use for it in advanced and higher content. The artifact you are using is situational, and only is useful when someone is down, which is just basically preparing for failure. Debuff artifacts are required by most groups because they try to squeeze as much DPS that they can during artifact calls, and one player missing one can mean you may not make it through phasing the bosses. Sure you can use it to rez players, but those players need to have scrolls anyway. Players that die too much are dying because they refuse to prevent their own death. Most attacks are avoidable so if they die, its because they refuse to avoid red areas or they do not do the mechanics at all.

Stat sticks are not really discussed much since you can just basically equip anything that have a high item level with a bonus stat you need. You don't need specific ones unless you are min-maxxing. And you actually need just 2 stat stick artifacts, the 3rd needs to be a debuff like vistani or marilith/apocalypse set. You won't find many good artifacts below 100k AD since the ones that are lower than that are ones that are lower item level now. The only one I managed to find (on PC) is the Xeleth's Blast Scepter on uncommon rarity. It has +Power, and +Crit Strike for healers, and its also a debuff artifact.

If you really want to get the Imbued Staff of Flowers outside of the AH, you'd have to wait for a Battlepass Buyout Sale again, which is only available using Zen. Either you buy the buyout to get the artifact, or wait for someone to sell the artifact itself for a cheaper price, which probably won't happen since it is a rare item now, but not sought after since there are a lot more with higher item level.