If the ability to use a shield while TWF does not seem notably powerful in anyway, our view point differs quite a bit; that's fine, just not a lot of common ground we'll find there. My problem is that the narratively silly thing to do is the mechanically powerful thing to do, and it certainly seems unintentional that it works that way. But maybe they read the feedback, are aware it works that way, and thought it was fine! I've been told otherwise by people in this thread that read their articles, but I don't know their minds.
Oh, you were talking about the Dual-Wielding with a shield. Yeah, clearly not intended and I wouldn't allow it. Most players wouldn't think it was allowed either. This is very clearly a case of a rule meant to allow one reasonable thing, being used as a loophole in a different situation. Honestly, it would be easy to miss in my opinion. I certainly never thought about it until people brought it up with the book being released. I thought you were refering to the other weapon juggling "exploits".
I think this is a good illustration of why it doesn't really matter much if it is intentional or not. What matters is the outcome and the quality of the content, and many problems the DM will have so smooth over. If you thought 'oof, really' and found whatever it was was intentionally designed did that make you immediately think it was fine then? Probably not.
It's pretty much exactly my point that WotC should be aiming for at least the same standard as homebrewers or 3rd party content creators (and probably much higher). Imagine the show that would ensue if someone like me posted Giant Insect as my shiny new creation and how people would line up around the goddamn block to explain to me that I didn't understand basic game mechanics.
Either the interactions were intended, and it's terribly balanced, or they were not intended, and its terribly balanced. It's at very least a game warping mechanic that all encounters the DM designs will have to account for and design around in each important fight, which is pretty much my benchmark for broken, at least when it comes to a spell.
If I wrote the sort of things that were busted in D&D 2024, I would be happy to have some bloke like me diligently compiling the mistakes so I could review them... and in fact that exact thing is almost always happening; there's google sheets for just that thing out there. In theory, that's what the UA was, but not only did many things change from the final UA and never get reviewed, they didn't seemingly address the ones that were caught in UA.
Did I suddenly think they were fine? No. Have you literally changed every single rule you wrote that anyone called out as being too powerful? No, you haven't.
And your only issue with Giant Insect is that it bypasses Legendary Resistance. You wouldn't have an issue with it stopping The third troll that the party is fighting along with his hobgoblin archer back-up, would you? And the designers wanted it to be an attack that does damage, and stop movement. They might have looked at that, and figured that with the design changes they have made to legendary monsters, it was good, but not game breaking. Or they might have copied a monster statblock, and not even considered it being used against legendary monsters, which is a little sloppy, but I'm not sure I can blame them. I usually end up with only two to three legendary monsters in a multi-year campaign, usually just one at the end. Additionally, even legendary monster fights at WoTC have minions and other monsters in the group, so maybe they didn't see it as a problem if the party could lock down the monster for one turn. Even more additionally, reducing a monster's speed to zero is only bad if you end up out of melee reach, and the general consensus I've been seeing is that melee is better and more desirable than ranged now, making that even less likely.
The Giant Insect is a summoned creature, it uses your spell attack roll. So... yes.
You'll find when looking at 5e 2014 spells that no high level spells use a spell attack roll (and for that matter, and D&D 2024 spell besides summons), and spells that do tend only do damage. This is an intentional design, because you're not intended to be able to debilitate a creature through hitting its its AC. Again, that's why Legendary Resistance exist in the first place. Saying it can rely on its AC would be same as 'why can't it rely on its saves?'
The Sentinel Feat. It now allows the attack you make as a reaction using it to be an opportunity attack, meaning it applies the zero movement buff (I guess it didn't before, technically) so we have to remember that locking an enemy to zero movement with a single attack roll and no save.... does already exist.
And it is interesting that you mention high level spells, because LOW level spells do allow this. Glimmering Smite, Blinding Smite, Ray of Sickness and I'm sure there are others. So... are all of those also problem spells? Are those also unintentional?
As for just accepting the monster cannot move... The only high level 2024 Monster I've seen (the Adult Green Dragon) does not have much it can do to PCs that are >30 feet from it. It's Breath Weapon is 90 feet, and it has a few spells, but outside of that its helpless if it cannot get within 30 feet of it's targets. It's offensive CR is halved by being unable to move and its most dangerous interaction is entirely eliminated, which would make it a fairly trivial fight. A CR 22 creature should have its CR halved by a level 4 spell. That might be a subjective opinion, but it seems pretty reasonable an ask to me.
Its only powerful ranged Legendary Reaction (the new version of Legendary Actions) triggers on using Legendary Resistance... which this would never trigger. It certainly does not seem to me like WotC is designing around the possibility of easily dropping a CR 22's monster's movement speed to 0 to me.
You need to read the dragon more carefully. It triggers on a legendary resistance... or being hit with a ranged attack. Also, "a few spells" is pretty disingenuous.
While the more than 30 ft might still cancel the Charm Monster (unless the spell's range was increased) it doesn't prevent the Dissonant Whispers which is 6d6 psychic and a forced movement, or the Cloudkill which is 8d8 and provides heavy obscurement meaning that nothing can see the dragon to target it with ranged attacks.
Is it less effective? Sure, but since it can level that playing field with a single action to make it so the party can't hit it either, I'm not exactly worried about Giant Insect dominating that fight.
The giant spider summoned by Giant Insect is not the Monster Manual Giant Spider block. It is a custom statblock for the spell (thats how it uses spell attack to hit and has 70 hit points and all that). There is no reason for it to use monster mechanics. It only exists in the context of the spell, and is a PC facing ability.
So you have seen the 2025 Monster Manual and can confirm that the web bolt ability does not exist on the Giant Spider in that book?
I don't know where you are getting this. Everything you described still works with the D&D 2024 Spirit Guardians.
It triggers "whenever the Emanation enters a creature's space AND whenever a creature enters the Emanation".
Ah, that was not how it was explained to me. It still doesn't activate again at the start of the creature's turn, so it will usually end up being half the damage it used to be.