Thorns Potion

The reflected hit is nice and the shove is what actually keeps you alive. Anything that touches you gets thrown a long way, which breaks up the pile ons that kill players in melee range. Treat the buff as crowd control with a damage side effect rather than a source of damage.

It earns its slot in fights built around bodies running into you. The swarm the Brain of Cthulhu leaves behind is the obvious one, and the phase where Queen Bee stops shooting and starts charging is another. Against anything that attacks from range it does nothing at all, so it is a situational bottle rather than part of a standard buff round.

The turtle set bonus replaces this effect instead of adding to it, so wearing that armor makes the potion pointless. It also overrides the Dryad's protection, which is easy to forget when she is standing in your arena during an invasion. Cactus armor is one of the few things it genuinely stacks with, though that pairing is a long way behind you by the time you can brew these in bulk.

Banners cut the damage an enemy deals to you, and the reflection is calculated from what you took, so the same banners quietly reduce what goes back the other way. It is one of the rare cases where more preparation makes an effect weaker.