Spirit's Whisper would be fine at common in multicolored set with token theme in WB faction/archetype (you probably don't put multicolored Mind Rots in normal set anyway). Thought Drain could be common too.
I don’t really like Mental Assault mainly because it will be used as Char in most cases. Forced Disencumber is my favourite card from this „cycle“ and I would love to see it printed.
Sworn Confession is pretty obvious design and I'm sure it will be printed once (which doesn't make it less cool). Memory Scour would easily work at common if it just milled for two. Hazard Fume is probably too strong in limited for 1BB, it needs to cost at least 2BB, maybe even 3BB. Also "up to one" part doesn't make any sense, because when you don't target a creature, the spell does nothing. Blightning looks pretty inelagant after the rules change, I'm sure that if they want to print card like this again, they would use Carnival // Carnage’s wording. Unburden Thyself is fine, but maybe little boring. What about making it +1/+1 for each land card discarded this way (or even this turn)?
Considering it's basically equal to draw three when you cast it from your library, it might need to cost more. On the other hand it's not that easy to abuse this without access to cards like fetchlands or other cheap shuffle effects like Open the Gates and there is always risk of drawing it as overcosted Divination (which isn't really good card even at three mana) therefore it's probably fine.
Thought Drain could be common too.
I don’t really like Mental Assault mainly because it will be used as Char in most cases.
Forced Disencumber is my favourite card from this „cycle“ and I would love to see it printed.
Sworn Confession is pretty obvious design and I'm sure it will be printed once (which doesn't make it less cool).
Memory Scour would easily work at common if it just milled for two.
Hazard Fume is probably too strong in limited for 1BB, it needs to cost at least 2BB, maybe even 3BB. Also "up to one" part doesn't make any sense, because when you don't target a creature, the spell does nothing.
Blightning looks pretty inelagant after the rules change, I'm sure that if they want to print card like this again, they would use Carnival // Carnage’s wording.
Unburden Thyself is fine, but maybe little boring. What about making it +1/+1 for each land card discarded this way (or even this turn)?