Allowing buffs to stack would create balancing nightmares that would result in jobs like WHM, SAM, and BLM (i.e., jobs that do not offer party buffs/utility) dying a slow, painful death as they are ousted from optimized settings. This already happens with two of them (WHM, SAM); BLM has just now managed to make it back into some of the top speedkills THIS tier because the developers finally allowed it to do enough damage to make up for its lack of utility—they’ve never been good about balancing utility jobs against “selfish” jobs, and it has shown for quite some time now. Do you understand this? Because I don’t think that you do.
That said, communication isn’t necessarily needed to avoid overwriting. Paying attention is—but that’s necessary to complete content, anyways.
This happens to everyone at some point or another. It’s happened to me as well—I’ve been overwritten and I’ve done the overwriting. Generally what happens is the AST that made the blunder apologizes, and people move on. Overwriting cards isn’t nearly as big of a deal as you’re making it out to be because the content that this usually occurs in does not matter when it comes to balancing. Balancing only needs to be done in high-end settings; not in leveling dungeons.
The fact that the developers already don’t do this is why we have balancing problems now—see BRD/MCH and the piercing debate. Why has BRD/DRG or MCH/DRG taken up two meta slots since Creator? Because the developers don’t understand the way optimized players work; they don’t understand that BRD/MCH will always want a DRG for their piercing debuff because that is 5% of their damage (much like how optimized groups will want AST for that +5% AOE Balance over a WHM that offers then nothing). They don’t balance around piercing when they balance BRD and MCH against one another, and this is why the physical ranged have always ended up better than the casters (particularly BRD—this is an even larger issue with it because they don’t consider how critical hit-enhancing buffs interact with its Repertoire mechanic).
I don’t think you understand any of this, if I’m being honest; and that’s why you don’t understand why people are disagreeing with your suggestions.
Unwillingness to communicate, educate, or cooperate does not equate bad design. Stacking cards and allowing other buffs to stack IS bad design because now the jobs that don’t offer buffs—or who offer weak buffs—will suffer even more. Because players that want to min-max will take the jobs where they can stack buffs. They already do this without the stacking.
The solution is simple. This is a non-issue for the majority of players. If you can only plug your ears against those telling you that your solution would cause issues of its own, then we are no longer having any sort of meaningful discussion.
Sure. I suggest that cards (and other buffs) remain as is—they don’t need to stack.
EDIT because I saw an edit:
Diurnal AST HoTs do not stack the same way WHM HoTs do. They never have. That's why you don't see two ASTs both in Diurnal Sect for things - one is always Diurnal and the other is always Nocturnal. And that's not because of a "shields are needed" thing either (shields aren't needed for anything other than high-tier Savage and Ultimate); it's because AST regens do not stack with one another. CU’s HoT also does not stack if you have two ASTs. None of their buffs stack, except for maybe Synastry (and I wouldn’t be surprised if it didn’t).
I literally just tested this with a friend—we were both Diurnal AST in a party and our regens (both Aspected Helios and Aspected Benefic) overwrote one another’s. They do not stack.