Is it possible or worth it doing quests marked as red in Witcher 3?

I'd say it's not worth it.

Even if it was true that the weapon is slightly more OP, there is no point torturing yourself with 30 minutes of dodging and doing few points of damage. Why?

• The weapon/armor you will receive will almost certainly be locked out until you get the level that the quest actually required, so you will end up carrying a huge piece of metal in your backpack/chest that you won't be able to use at all, and with stats that might be scaled for your current level.

• As I did some research, most sources say that weapons and armors do scale, but with crappy random rates, and you will never be sure what this 30 minutes of dodging will give you.

Why don't you want to fully enjoy what game has to offer and do other (non-red) side quests or proceed with main plot? And when you have higher level the previously-red-quest is going to be enjoyable too... So unless you are some kind of masochist or achiever, I would discourage such gameplay.

It is not worth it for the gear. However, you might get more XPs doing the quest. This might be a quicker way to level. Although, there are plenty of questions at your level which provide XPs aplenty so even that does not sound like a good reason to slug it out.