I think this is all of them

WHM+WHM regens, AST+WHM regens, Stoneskin+(Galvanize OR Nocturnal Field)+Divine Veil all stack. WHM regens can stack indefinately! 8 WHMs can get 8 Med2+ 8 Regens going on them. Diurnal regens can stack but only Asp. Benefic + Asp Helios + Collective Unconscious, so diurnal Asp Benefic from two different ASTs will not stack.

Galvanize + Galvanize does not stack (stronger will overwrite the weaker)

Noct Field + Noct Field does not stack (again stronger will overwrite)

Noct Field + Galvanize does not stack (they will ALWAYS overwrite each other, even a crit Adlo can be overwritten by a Cleric'd Noct Aspected Helios)

Eye for an Eye does not stack with itself but will stack with Bole + other defensive buffs

AST cards do not stack and will always overwrite (e.g AOE Spear will overwrite Enhanced Balance)

Sacred Soils do not stack but Soil does stack with Collective Unconscious

Virus + Disable can stack

Bole + Fey Covenant (Eos' magic defense buff) stack