First time playing in many years. I remember spending so much time trying to get Blue magic, but I'm just going to run through the story this time. It's not like I need the extra help, I seem to be 1-shotting everything with this Ogre, Vivi's magic, and Freya's jump.
Is there anything I would miss out by missing out on Quina? Except for the character of course... like anything story related? Any sidequests? Unique cut-scenes or conversations?
I'd say just get him as early as you can. More dialogue, more ATEs and (as mentioned) even a little treasure. It's not like you lose anything by not doing so, as during the time he is optional, there are no moments in the game where you could choose someone else in place of him.
If you don't want to bother with blue magic, then you can have him as a healer, throwing Phoenix Downs/Potions etc. Then there's also Add Status + Needle Fork if you are feeling lucky, but other than that, I really wouldn't rely on the random damage of his forks.
Obviously if you don't like Quina or don't want a comic relief character, then don't get Quina. But like edubs said, at one point you must have him.
If something is frustrating, then it's hard. There's no "it's not hard to do, it's just frustrating" in that case it's hard to do due to frustration.
Not much those 2 chests contain items you can make yourself later on anyways but still since Quina is forced into the party mid disc 2 its still best to learn all possible blue magics ASAP so still get him/it to join on disc 1.