I have a (as far as I know complete) list of attack speed stacking here, should you want an overview: https://forums.obsidian.net/topic/88795-trying-to-figure-out-casting-speed/?p=1837581

Good stuff!

I checked, Circle of Defense indeed uses the 'all defenses' stat, so will stack with individual bonuses.

Making it a great spell.

Yeah it's the same reason why Form of the Delemgan (individual DR buffs) works with univeral DR buffs, making it a really great spell.

Inspiring Radiance is another exception as the accuracy buff does stack with other sources of accuracy.

Same with Aggrandizing Radiance and most other talents that add some special effect to an ability.