About irony/sarcasm: I used to think exactly like you. I must say it was totally flawed. I don't know how to word this scientifically (and please understand I'm not religious): sarcasm hurts your soul, your heart, your mind, your spirit. It's like drugs: short term good but really bad long term.
It helps for some time and then slowly eats at you. A sarcastic person is in effect trading the possibility of hope for the comfort of accepting things. There is a way where you keep both, through forgiving, through understanding, with humility.
Humor gets a pass when it speaks of bad things, or in a bad manner, because it's a way of denouncing said things/manners. Certainly not to validate it. That's where sarcasm has its place IMHO: as a very bad manner that humor serves to show.
About Stoicism: that's true. Hence why I always preface with self-love, because the Stoic apparatus is quite unable to speak of this in modern terms. In general I agree with Ferris on this though: Stoicism is the best operating system for the human mind. Now that I know, I see it and find it in so many things, people, the good side of life (and it seems quite missing in many a miserable path).
This is a perfectly fine coping mechanism for big-picture stuff (environ. protection, climate change, genotoxic materials, migration, politics); it only becomes highly problematic when you use it as the coping mechanism for everything.
> Stoicism
Depending on the construction stoicism can come quite close to nihilistic world views, actually.