About Goddess' Blessing play style:

It's the talent where Io doesn't need Luna, Io is very independent.

For me it's the talent that lasts the longest in the game among the other 2. Because if an enemy takes Bulldozer, with Life Link you can no longer put Luna on the front line to heal tanks. As well as the damage reduction has no counter where Life Link has Cauterize...

With this talent Io is very greedy on Moonlight. You should even heal when the allies are under Cauterize! Thanks to the damage reduction and the Swift Arrows card you can easily help an ally out of combat.

Even use Moonlight before combat to get an ally on the offensive, or avoid lethal enemy fire (Strix, Kinessa).

So with this talent you could ask yourself how to use Luna as much as possible.

How to position Luna in my game ?

First of all, Luna's position is between the backline and the frontline. With Luna you need to stun as much as possible. The easiest targets are tanks (your stun and ult shut down their shield).

Luna works like a turret when she does not have a stun and provides constant damage.

When Luna no longer has enough HP (~20%-30%) puts her in backline for her to regenerate herself.

Quite often you will have to predict in advance when Luna will die or if there will be a flanker because repositioning Luna is slow.

One of the strategies for easy stun is to have Luna in an isolated place, shooting an enemy you want stun and finally teleport Luna near that enemy (it works well when you want to stun a flanker that will attack you).

So if we can summarize this:

Luna is in a safe place->you shoot the enemy you want stun->you teleport Luna to that enemy->you use Moonlight to reduce cooldown time with Spirit Arrows->put Luna in a safe place (repeat).

Sometimes Luna on point is also really good if there is no tank in your team that can go on it due to a sniper for example.

A final tip:

Since the last patch with the Moonlight buff (Moonlight has a small window of 0.8sec before the link breaks) switching from one ally to another seems strange and sometimes difficult. I recommend to put Moonlight on another key or spamming Moonlight on an ally to get out of another.

Like putting Moonlight on the left click looks a lot like Mercy's heal in Overwatch (but don't feel as great as in Overwatch :/ ).