As healer im going to state that the dps kits of all 4 must remain quite similar. Otherwise it creates a big vulnerability in which a healer can become dominating by having significantly higher dps than others. Which should be avoided. This means the 1111 is most likely going to remain a significant part (and i actualy think that is fine).

I think the focus should be more about giving the dps some extra skill potential by simply making 1111 alone not cut it anymore. SCH might have a few charges it can spend on dps. But its a minimal effect as you often want to preserve the charges for actual heals (extremes and unreals demand enough here already, so if you can use the charges, it feels as a reward enough).

But this means 2 dps buttons chained in each other. And idealy introducing a condensed system here so it can be expanded later without changing too much. ie: at lvl 100 you have 112112112 as optimal combo (the 2nd 1 cast triggers the other ability to be available), but at 110 it could be 1121211212 (chain is expanded to 3 where the other one now has 2 abilities it can chain into). It keeps the buttons compact here, which to me is still an important part. We dont have room for many dps abilities. Maybe at 105 you also expand the AoE to also trigger into that combo, giving that new button a potential 3 diffirent abilities as outcome). Its a quite future proof way to expand the kit.
Difficult? not realy, but it allows the minimal improvement in dps that is still desired as a skill measurement system.
(and yes, 220 main potency and 300 on the 2 cast is a fine enough value to work with, proper chaining then means about 20% higher dps which is fair enough without forcing too much distraction)

If healers get a 123 combo that must be repeatedly pressed, thats just going to be anoying when they want to add more conditionals, as that means condensing has to happen again. I rather have them be ahead here and introduce the condensing earlier.