SCH is anything but bad, it's actually still part of the meta comp. It's just not as fun to play outside of raid/extreme primals content. The buffs upcoming will likely address the clunkiness of the new skills and it's snoozer of AoE DPS. The cost-benefit of skills ratio compared to Astro is what got some people going crazy. Noct Astro needs to have more potent shields because they don't have any access to regen, no shield deploy, nor does it have any free mitigation debuffs from Eos.

Regardless, AST/SCH is once again going to be the optimal raid combo. You have to remember every other tandem that doesn't include SCH has to always "manually" heal. You can talk shields all you want but a Noct Astro doesn't bring a free healer that flies around and has really good cooldowns that don't cost anything. A brilliant strategist will take full advantage of them, every fight, and put good damage on-the-board which also helps the other healer not have to heal as much.