Any healing team without a SCH is going to be sub optimal because it is simply so good at it's role. That being said, any of the combos are workable. One thing you may run into in your setup is WHMs dpsing can run into mana issues, and AST also have mana issues in marathon fights - you may be relying on some good luck Ewer RNG to ensure each healer gets one or two. The other thing you are missing is the massive AOE shielding capability of a spread Adlo + Fey Covenant - although I am unsure how much it will be needed in this raid tier.