What stacks and what doesn't?

Hello! This question is going to sound very uninformed, because I am very uninformed here. I'm approaching the Job mark on all my classes, so I will start playing around with WHM and SCH (AST eventually) soon. Now, I periodically see stories or rants about people overwriting each other's buffs or shields or regens or what have you. Rather than become a story for Reddit, I'd like to nip this in the bud:

What stacks, and what doesn't? What overwrites? What just overlaps? I know this is vague, but my knowledge of healing classes is rather limited outside of the buffs I see on myself while tanking, and that hasn't helped me figure this out.

Edit: and while I'm here, does the PLD shield from Divine Veil stack with healer shields?

Yes, PLD Shield stacks with healer shields. Astro (Noct) and Scholar shields don't stack with each other (they'll overwrite), but both stack with Stoneskin. All different types of Regens stack with each other (and you can have more than one of each up at once on one player). A player can only have one Astro card up at once, so those won't stack.

All Heal over Time (HoT) effects stack with all other HoT effects from other healers. For example: WHM 1 casts Regen on the main tank and Medica II. WHM 2 also casts Regen on the main tank and Medica II. The main tank will have 2 separate Regens and 2 separate Medica II actively healing. So that's a total of 4 HoTs going at once. This includes all AST HoTs while in diurnal sect.

All shields from SCH and AST (nocturnal sect) overwrite all other shields from other SCH and AST. Example: SCH 1 casts Succor on the party. SCH 2 then casts Galvanize on the main tank. The Succor shield would be overwritten by the Galvanize shield.

As for buffs? This is mostly referring to Card buffs from AST. All card buffs will replace any preexisting card buff. Protect also doesn't stack, so only one person needs to cast it. Same with Stoneskin.

The basic rule is: HoTs stack, everything else doesn't. Though, there are a few exceptions (Eye for an Eye stacks iirc).

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

Kioku's thorough reply is correct, and quite near complete. Additionally,

Arrow + Fey Wind (Selene's Haste buff) stack.

If two ASTs use Collective Unconscious, the damage reduction is only applied once and only one regen applies, but if a party member stands in either bubble at the time the server ticks, the duration of the regen will be restored to max (15s).


The behavior of the AST regens is noteworthy here because two separate ASTs cannot both put up all their regens, as was suggested in previous replies.