Keeping in mind that 60s cooldowns are up for every pull and alternating 2min is a good approach.
It's much easier to handle a pull that is mostly taken care of by oGCDs and only having to use some GCDs worst case than fully oGCD'ing one pull and then being reduced to GCDs only the next pull. Like mitigation, spread them out a little but because SGE is weaker than other healers when GCD healing as they lose the Kardia heal potency. So a Diagnosis is technically 270 potency from losing the Kardia heal before 85, not 400.

I'd also like to add that Krasis and Autophysis (the heal buff) affect Haima and Panhaima.
Haima is already incredibly strong as it is, with 1800 total potency unbuffed it's like a mini tank invuln while it's active. With Krasis, it can reach up to 2160 potency depending on how fast it gets consumed. If you apply those skills in proper order (e.g. Krasis > Physis II > Haima) you'll get more value from them.
It's a fairly minor thing but try to make it into a habit.

It's also a good idea to make sure the tank has already lost some HP before applying Haima/ Panhaima as these skills prevent further HP loss but Kardia and regens will continue to heal and have a high chance of overhealing if you instantly throw them up at full HP. Your aoe is instant so you don't have to worry about missing the right timing to use them.
I often go:
Kera > 1-2 GCDs (> Krasis at 86+) > Physis II > Haima/ Panhaima. That way Haima/ Panhaima get the heal buff and the Kardia/ Kera/ Physis regen won't get wasted.
They're all minor things and SGE is fine without doing it but practicing it will make healing easier over time.

Having access to non-stop 10% mitigation and several oGCD shields makes incoming damage a lot smoother and easier to judge and decide what you need to do. I agree with ty_taurus, SGE maybe overwhelming at first, partly because it starts at 70, but I find it overall the easiest healer.
Easier than WHM as WHM has to deal with much more erratic HP bar pingpong in wall to walls, having longer gaps between oGCDs from Holy being 2,5s and often losing value if healing too soon. It's not difficult per se but the HP bar pingpong makes it easier to misjudge, lose confidence and then just spam safety GCD heals rather than trying to risk anything again.