See, but who's gonna remove their Meteor stuffs to wear some cactus to get thorns(and a low 5 defense)?
And Even early game, 5 defense can be gotten from accessories, e.g. Warding Shackle
Cactus is meant to replace copper and iron for the speed runners who need defense and don't have time to mine.
So, adding the Thorns is logical. (Though Terraria is all about "screw logic")
In a sense, getting cactus is about the same challenge to get copper/iron.
To get copper, you need a lot of copper and around 15 iron ore. Not to hard.
To get cactus and ebon/shade wood, you have to explore 2 potentially dangerous biomes with mobs more powerful than you are, so surviving these rewards you equally.
And about farming cactus... By the time you've done that, you might as well keep the farm for the pink prickly pears, because that armor is only something to put on a mannequin.
Now about your fix...
10% increased damage? It works... this gets OP later, but as I said before, who's gonna get cactus for this?
3% chance to inflict Poisoned! To both the attacker and the defender
This is weird. 1) This debuff is the annoying debuff given by Dart Traps. It does little damage, and is an annoyance to the OCD freaks (me) who have less than max health. 2) It is not going to do major damage to anything unless fighting the common zombie or skeleton.
That's me trying my best to defend this suggestion...
Also, spelling errors.
(Whoops, forgot my support! 11/10!)