First goes into Invisibility, runs towards Lae'zel and shoves her into the lava. Oh bugger - she was too far away from it, and didn't quite make it there.
No worries, second Duergar repeats the same process, and now Lae'zel successfully lands into the lava. Insta-death.
As of now, the action economy allows them to do that in a single turn, and Shove being guaranteed if executed by an unseen character doesn't improve my survivability either. If Shove will ever become a full Action, they will only have to change their tactics slightly - everyone goes to Invisibility on their first turns, then on the next come Shoves aplenty. And what countermeasures I have against invisible enemies? Bupkis. In BG2, Glitterdust worked wonders in such scenarios, but we don't have it here.
Its cute that you are dementing your own example ...
But exactly as you said ... there is zero relation to potion throwing, so ... w/e i gues.

Dont be mad at me, if you have any other scenario in mind, please share ...
Even so amazing and flawless (kidding) creature like me can potentialy make misstake, so its possible that i forget something.

But right now ... no matter wich side im watching it ... it seems to me like throwing potion would be the most uneffective thing you could do in combat, IF at least Larian would delete that part where potions have effect if they miss ... after all, that hit chance is in fact substitute for catching roll.

When your party is outnumbered like 12:4, your best option is to find a terrain chokepoint, use it as a force multiplier (same as the famous battle at Thermopylae) and
concentrate on one enemy at a time (because, obviously, a Duergar with 1hp left hits just as hard as one with full hp). Current implementation of potion throwing severely disrupts this strategy, so it's not as daft as it looks.
Same as abowe ...
I mean yes chokepoints was indeed often used scenarios in many military situations in our world ... but i see no relation to that suggestion i posted. O_o
So ... no idea what were you trying to say here. :-/
Sure, several ...

So the question was wich spells can be casted only by caster and not by any scroll or potion right?
(Yes im purposely ignoring Magical Artefacts that allows us to cast spell once per Long Rest.)
https://baldursgate3.wiki.fextralife.com/Dancing+Lightshttps://baldursgate3.wiki.fextralife.com/Eldritch+Blasthttps://baldursgate3.wiki.fextralife.com/Friendshttps://baldursgate3.wiki.fextralife.com/Shillelaghhttps://baldursgate3.wiki.fextralife.com/Thaumaturgyhttps://baldursgate3.wiki.fextralife.com/Thorn+Whiphttps://baldursgate3.wiki.fextralife.com/Burning+Hands (Not sure here ... but i dont think i have seen scroll, could be misstaken tho)
https://baldursgate3.wiki.fextralife.com/Dissonant+Whispershttps://baldursgate3.wiki.fextralife.com/Faerie+Firehttps://baldursgate3.wiki.fextralife.com/Hail+of+Thornshttps://baldursgate3.wiki.fextralife.com/Hellish+Rebukehttps://baldursgate3.wiki.fextralife.com/Tasha's+Hideous+Laughterhttps://baldursgate3.wiki.fextralife.com/Thunderwavehttps://baldursgate3.wiki.fextralife.com/Cloud+of+Daggershttps://baldursgate3.wiki.fextralife.com/Darknesshttps://baldursgate3.wiki.fextralife.com/Crown+of+Madnesshttps://baldursgate3.wiki.fextralife.com/Darkvisionhttps://baldursgate3.wiki.fextralife.com/Enlarge+-+Reducehttps://baldursgate3.wiki.fextralife.com/Enhance+Abilityhttps://baldursgate3.wiki.fextralife.com/Heat+Metal (I believe i have seen this one in previous patch, but not anymore)
https://baldursgate3.wiki.fextralife.com/Moonbeamhttps://baldursgate3.wiki.fextralife.com/Pass+without+Tracehttps://baldursgate3.wiki.fextralife.com/Protection+from+Poisonhttps://baldursgate3.wiki.fextralife.com/ShatterIs that example enough?

Also note that every single scroll that is in game can be easily added to this list with condition "upcasted" since scrolls (as far as i know) contain only lowest possible spell level.

One little problem, however: practically all Cleric's buffs require concentration, and they can't concentrate on more than 1 spell at a time. If I find Shadowheart in a bit of a fix, and decide to put on Shield Of Faith - here goes my Bless for the rest of the party.
Therefore you should not do that.

Also this "problem" for lack of better therm ... is part if Cleric design from WotC ... that is not something we should blame Larian for ... therefore its not quite relevant for both this forum and this topic talking about potions.

Also, did Larian fix it, or does Cleric still lose concentration on any surface damage, without a DC roll? I remember seeing Lae'zel rolling DC for her Shield Of Faith, but don't remember about Cleric.
As far as i know they are rolling ...
Most people complain however on the fact that they are forced to roll a lot more often than in tabletop.