It isn't pleasant to use, it causes more harm than good, and definitely doesn't prevent toxicity.
Please, just let us have normal chat like every single other time (dungeons, raids, trials, FRONT LINES, literally everything else.) The Quick Chat is good in theory, and can even complement the standard typing system, but it isn't good at all by itself as a base thing.
The Quick Chat is severely limited, has so very limited options to even attempt to communicate an intention, and worst, it doesn't even have good options. Sure saying "Attacking <job>." can give an idea, but what does it mean? Does it mean you're going to chase them into LaLaLand, does it mean focus fire, does it mean, "That's the person that killed me."? Just a few examples, but it lacks the nuance.
The fact that I can't type something as simple as, "Focus NIN then DRG." in chat bothers me greatly, and considering we can already do this in other PvP modes, bothers me further. I really don't know what else to say, except please just give standard typing back, and let Quick Chat just be a complement system, and not stand-alone.
To address a few things I guarantee will come up:
1) But it stops toxicity and tearing people down.
1a) Not really, people are able to spam the 'positive' things just like they do in every game that has this kind of system.
2) Quick Chat spammers are getting punished, so this stops toxicity.
2a) You know what else hands down punishments? The report system on the Help Desk. Super simple to fill out, requires minimal effort on your part, and you too can battle toxicity in typed chat.
3) Everything you need to say is in Quick Chat in some form, just get good.
3a) Read above, things can have many intentions, and honestly with how terrible some of these players are in CC? I'm glad they're having fun, at least I hope they are, but the simple fact that there isn't a clear 'Shot Call' option at all. Barest minimum let us create our own Quick Chats with 'approved' words.
4) What approved words would you even suggest then?
4a) Focus target, Stop chasing, Buffing <target>, Debuffing <target>, and others I'm sure people can think of.
Side tangent, please make seeing who you're targeting not such a pain. You get this tiny indicator of who you're targeting on the character model, and a 'highlight' on their enemy list. Can we please just have a health bar or something far more noticeable?