Ah, cast time abilities. Those threw me off. I see cast times, I think GCD, seeing as only Blue Mage has OGCD casts.

Instead of channeling, I'd suggest just doing longer than average cast times if you want to get the 'rooted to the ground' flavor. Cast time spells have all the same weight and problems that channeled do, but it's A) All or nothing, and B) A little easier to plan around.

Channels, especially those with a cooldown, are notoriously frustrating in a game where windows of opportunity often coincide with random forced movement.

My primary suggestions would be

1. Changing the nature of the filler. The GCD is 2.5 and Server ticks are 3.0. I can see this being a little off kilter. Nothing wrong with Shadowbolt.
2. The DoT reduction from the filler can be repurposed into a separate short CD ability (30-45s) that has a similar function, with a more pronounced effect as it's no longer on not-shadowbolt.
3. The Demonform timer seems unnecessarily short and likely a product of having the comparison from WoW. 10 seconds is an extremely small window of capitalization in FF14. 20-30s is more in line with FF14's pacing, and adjust auracite gain and Summon length accordingly.