I disagree that avoiding GCD healing is healer "depth," but rather a glaring flaw with the way healing has developed. I don't think GCD healing should always be free, but like with WHM, we should have ways to be rewarded for particular useage. The TBN nature of SGE currently is good in theory, but problematic on something without a cooldown because it means if Addersting becomes neutral or a gain, you stop using Dosis III in favor of using Eukrasian Diagnosis as much as is possible, and auto attacks break it on the tank very quickly if it's not a crit. If our goal is to not use them, then why should they exist in the first place? Every action should have a reason to exist--one that contributes to gameplay rather than take away from it.
Also, we regularly discuss wanting more to do other than Glare/Malefic/Broil/Dosis spam, and to not always be DPSing for 99% of our GCD usage, which is exactly what this would promote.
That makes sense in theory, but it means that Toxikon II either is a separate button or it replaces Toxikon automatically. Then the goal of pruning Dyskrasia has failed. If it's automatic, it creates a weird situation where your normal AoE button converts into something with a cooldown by force and removes your ability to use Toxikon as a mobility tool while active if you want to preserve Addersting. I think it's a bit simpler to have Toxikon II be its own button and remove the Krasis Dyskrasia reset aspect, but I kind of liked that interaction.
In ARR and HW, Ruin II's potency was DPS neutral but had a higher MP cost which was a perfectly fine and well-liked mechanic as it gave you movement and additional weaving for an MP tax. Having it be weaker I think makes it just feel bad when you're forced to use it rather than feeling good about your ability to keep up your DPS and keep your GCD rolling during movement-intensive mechanics. SCH at least has Energy Drain to make up for the lower potency, but it's not a foolproof system. It also compliments the goal of raising the skill floor because a more frazzled, newer healer doesn't have to lose DPS if they rely on it more to maneuver a chaotic fight. They may spent too much MP, but then they have Eudripsia to rely on.
Since the combo spender has a 60 second cooldown, but you could theoretically generate 1 Addersting per 30 seconds against a single boss, that means you have Addersting to spare to get off barriers and refund your lost DPS, but you also aren't obligated to do this other than readying yourself for your burst window. It's more about giving you the option to use Eukrasian Diagnosis/Prognosis without making it feel necessary for DPS optimization. You could, in theory, be alternating every 30 seconds. Toxikon > Combo > Toxikon > Combo... etc and double up during burst windows with Krasis' effect.
As for the splash, there's nothing particularly wrong with backloading AoE damage off a combo rather than spreading it around the whole combo. A part of it was also just what I envisioned as the animations with Cardiorrhexis and Cartiotomy being precision lasers and Paroxysm and Sarcotripsy being rapidfire spreadshots.
Krasis is used on cooldown but offers no healing on its own. It's simply enabling you to use up to 2 Holos casts over a 2 minute window. During that time, both uses are GCD heals with your standard 2.5 second cooldown, so there's no pressure to use them specifically at any moment. They award Addersting and thus are neutral or gains for DPS, but you can always use Eukrasian Diagnosis or Prognosis instead so they're entirely optional for DPS optimization while also giving you a bit of room to generate extra Addersting which you can use the excess of since Dyskrasia's cooldown is 20 seconds rather than the 30 second duration of Eukrasian Dosis III. It's really just about freedom and flexibility.