The SB cards are the only case where I'd say support cards could come at the cost of DPS cards. It would be possible to have as many DPS cards as we did in EW with the current system if draw's CD was reduced or if DPS cards auto refilled a couple of times.
As for the ranking of total healing values, I don't see why it's so important. There is always going to be a mix of contributions from different abilities and they won't all contribute an equal amount. The ones that top the list are more often than not the ones that can be used more frequently. Which ever skill ends up healing the most through the fight isn't necessarily the most important. With enough incoming damage any amount of skills can have a use. This is true even when it comes to DPS. BLM is a prime example. Fire IV is going to be the biggest component of damage because it gets cast the most. Despair, Flare Star, and Xenoglossy are all stronger and more important to get under buffs. A healing example would be Collective Unconsciousness. The HoT has a lot of uptime so it's going to rank high but that doesn't mean it's the only heal needed.
You're not limited to using a single ability at a time. Arrow by design only has value when combined with other tools. Your 400 potency shield can be a 400 potency augment of another shield and your 15 second regen can stack on another regen to speed up healing or sit on someone with a vuln up while you're waiting for something bigger to come off CD.Unless they massively buff the utility cards or give abilities that let you buff them during the fight, they are useless and will continue to be useless. You brought up an example of people making mistakes or having new players in your group but a random 400 pot shield or 15s regen isn't going to save them nor is it going to be your first choice when trying to save them considering how many better tools you have at your disposal. If you're so desperate that you need to use the cards to save them, you are most likely out of everything and about to wipe considering even a benefic II would do more healing.
There is a massive difference between performing correct rotations and applying buffs. The maximum damage boost that an AST could provide would be to maintain 100% card uptime on the entire raid with the appropriate cards. That would be 6% damage for the entire group. Over a 12 minute fight that's a difference of around 45 seconds. That's a lot, but card uptime is closer to 10%. So a realistic perfect AST is going to subtract maybe 5 seconds from a fight through cards vs an AST that doesn't card at all. To cross check that with data I looked up a random EW log on fflogs and the cards count for about 600 DPS out of 86000 in P12S. Any amount of DPS may be just enough to push the group over a threshold to skip mechanics but in most cases it takes a group effort and subtracting any single component doesn't change the outcome by a lot.It doesn't need to be a speed kill/ parsing group for the DPS increase from the cards to matter or feel significant. A freestyle samurai might do more than enough damage to clear a fight but someone doing their rotation properly would still help you clear faster and help you avoid later mechanics.
Randomly throwing out cards isn't going to feel impactful but if you know how many cards you're supposed to give out at the 1/2 minutes and time them with when people start their burst, it will add up and help you kill it faster, which in turn helps you avoid mechanics during prog/ reclears.
Even if we're talking about doing your last reclears and everyone having almost all the gear they need so you'd end up skipping mechanics anyway, what sounds more fun: i) Learning to spot when people do their burst so you can buff them and use your cards at the right time or ii) Have two cards that you play every two times that you always put on the same people every single pull?
When it comes to how cards are played since FF14 is so scripted card plays may end up being memorized which I don't find the most engaging, but I can understand the desire for it to return. Personally, having a lot of options for the support cards is about the same for me. I don't mind that they don't always have to be used and I actually welcome that ambiguity that the DPS cards don't have.
There are a few different opinions in that discussion. Some people want more healing buttons or an increased need to use the buttons we already have, which is something that EW cards can't provide. For those seeking more DPS options the cards could be counted as a solution as long as people were comfortable managing target swapping.Lastly, this is slightly off-topic but everyone complains about how easy healers are to play and asking for more buttons, which is fair, but Astro was the last played healer in Endwalker even though it was (arguably) the busiest and most complicated one until you learned when you're supposed to give out the cards. Is it a replacement for more dots/ dps abilites? No, but it sure is more interesting than spamming 1 and giving out a whooping 2 cards every two minutes.