So its a slightly worse version of feeblemind because there is now no reduction to INT and CHA scores, using magic items, Understanding language or even communicating properly.

However it deals more damage instead of 4d6. 

So the new version is more for combats against magic casters. whereas the previous was a blocker for all classes and uses of magic items but less damage. 

This one doesn't allow the Magic Action, which includes all magic items and spell scrolls.  It basically does the same thing as before, but doesn't affect saves, skills or language.  Still a nerf, but then more damage, so...

why is it avaiable to "Legacy Test Subclass", a barbarian subclass?

The problem with the old spell was that it made your intelligence 1, and then you had to succeed a potentially dc 16 saving throw or higher with a negative 5 to your intelligence modifier. This meant that without bonuses (and even with bonuses if the dc is from a high level caster, and it will be since they can cast this 8th level spell) it could be literally impossible to ever get rid of the spell without greater restoration, dispel magic, or some other remedy. In the mean time, you had to roleplay being a completely incapable character, and if your character was known for being charismatic or intelligent, you can say goodbye to any of that. It's still a very oppressive spell worthy of being 8th level, but it's nice that now it doesn't completely lobomotize your character, it just prevents using magic and does some good psychic damage.

Honestly I think the changes are to encourage it actually being taken by players. Pretty much every DM I’ve played with has banned the spell, and I can understand why.

Feeblemind  *   Legacy This doesn't reflect the latest rules and lore. Learn More Basic Rules, pg. 239

Link to the legacy version of this spell

* Spell was renamed from Feeblemind into Befuddlement.

Oh, just noticed another change that's easy to miss!

"On a failed save, the target takes 10d12 Psychic damage..."

"At the end of every 30 days, the target repeats the save..."

So this spell does 10d12 Psychic damage every 30 days until they save! Crazy!

Quote from zesban >>

Oh, just noticed another change that's easy to miss!

"On a failed save, the target takes 10d12 Psychic damage..."

"At the end of every 30 days, the target repeats the save..."

So this spell does 10d12 Psychic damage every 30 days until they save! Crazy!

The way I read this the damage doesn't repeat every 30 days - I think the target only takes the damage when the spell is first cast.  But the effect of not being able to cast spells or take the Magic action continues.  If the damage repeated, even if they made the saving throw after 30 days, they'd take 1/2 damage.

Well my table will still be using feeblemind, thank you very much. 

This spell isn't showing up as an option for my Bard. Anyone else?

Something no one has pointed out yet is that yes, while it does have increased damage, the damage here is affected by the saving throw, while the original feeblemind does damage that can't be reduced by succeeding the save. Feeblemine does the damage instantaneously, then asks for the save.

Losing the ability score is much worse for certain builds than just losing the magic action

bladesingers for instance still get all the bonuses for ac from int and psi warriors would still get the bonus for psionic strikes. 

No that’s not what it says. It says the repeated save ends “the effect” which is the inability to cast spells or take the magic action. The damage is a one time hit.