D&D 5E Aberrant Mind's Psionic Sorcery is officially the most powerful feature.

[Hohige]

It's not undetectable as I would also rule that a simple Wisdom (Insight) check is enough to determine if someone is doing something.

there isn't any direct rule about it on combat.
When you interact with an illusion, requires your action (Investigaion check) to perceive the illusion.
To find something hidden, requires an Search action (Perception check). On combat, all requires your action, unless descripted.
But here, It doesn't have any evidence about mind controlling.
As a DM. You certainly must use your action to roll a Insight check. But, without any evidence, I wouldn't call a Insight check.

 

[Savage Wombat]

I do find it strange that Tasha's suddenly gives sorcerers the bonus spells they should have been getting ever since the Storm Sorcerer saw print and didn't have them (even though it was in the playtest).

 

[Umbran]

To find something hidden, requires an Search action (Perception check).

Not true. There's passive Perception and Investigation. No reason why there cannot be passive Insight.

But here, It doesn't have any evidence about mind controlling.

People acting outside of normal expected behavior patterns is evidence of mind control.

 

[Kurotowa]

How did you phrase "turn on your allies in the middle of combat" as a reasonable suggestion, out loud?

It isn't totally undetectable. You still have to say the suggestion out loud. Maybe you can get around this with telepathy, but that doesn't get around the "reasonableness" of it.

Dominate person/monaster, on the other hand, almost does what you describe. You still have to tell them what to do (telepathically), or use your action to treat them like a puppet, so they do know that there is something strange going on.

And here's the real issue. It's not Subtle Suggestion that's overpowered, it's people treating Suggestion like it was Improved Dominate Person where you can order them to do whatever absurd thing you please. Which seems to be a distressingly common issue, from the threads you see on the Internet.

 

[bedir than]

Just avoid getting damaged and don't cast another spell requiring concentration.

You can concentrate on spells while doing most anything short of actually sleeping.

My understanding is concentration is enough to interrupt short rests as well.

 

[Charlaquin]

My understanding is concentration is enough to interrupt short rests as well.

There’s no rule to that effect, and in fact the existence of spells like Hex and Hunter’s Mark that can be concentrated on for 24 hours would seem to counter-indicate this notion. A long rest, on the other hand, would break concentration because it requires sleeping, and you have to be conscious to maintain concentration.

 

[JiffyPopTart]

No. the true power here is casting Suggestion with Impunity.
Being totally undetectable.
Low level, cheap and can still apply metamagic (Heightein, Twin, Quicken, Extend).
With Psionic Sorcery. The Aberrant Mind's Dominate Person/Monster can control a creature for 16h, with Impunity.
During a battle a Psionic Sorcery Dominate Person with Heightein Spell can literally win the battle to easily and control that creature for 1 minute. (No counterspelll)

For the enemy party, the creature affected by the Psionic Dominate Person is a traitor and he will start attacking his allies and even he doesn't understand what happened. It is beautiful to control a Barbarian and attack his backline.
Without any evidence of mind control.

Aren't you ignoring Dispel Magic in your anti-mind-control scenario. A much more likely course of action in my group would be to observe the party member acting strangely, detect magic on them, and then Dispel it (or use the ability of the Arcane Cleric to do much the same) when you noticed they are under an enchantment.

Just because something can't be counter spelled doesn't mean it can't be stopped.

 

[Kurotowa]

There’s no rule to that effect, and in fact the existence of spells like Hex and Hunter’s Mark that can be concentrated on for 24 hours would seem to counter-indicate this notion.

Indeed. Checking the PHB, the Concentration rules on p203 say nothing about preventing Short Rests, and the Short Rest rules on p186 only say it requires the PC "does nothing more strenuous than eating, drinking, reading, and tending to wounds."

This isn't the first time I've seen people confused about Concentration. In fact, at my own table I've had people who need reminders that Concentration doesn't cost an action or impose a penalty to other actions. I don't know if they're conflating it with mechanics in other editions or other systems or what.

 

[Hohige]

There’s no rule to that effect, and in fact the existence of spells like Hex and Hunter’s Mark that can be concentrated on for 24 hours would seem to counter-indicate this notion. A long rest, on the other hand, would break concentration because it requires sleeping, and you have to be conscious to maintain concentration.

Animal shapes is also 24 hours.
Extended Dominate Person/Monster/Suggestion is plausible

 

[jgsugden]

In play, there is no chance this is game breaking.