I can't speak for WalkingDad, but personally I have close to zero interest in running the encounters you describe here.
Its A
Rust Monster in one adventure over an entire campaign, I didnt say characters are too face
Rust Monster race as part of the campaign hook. But as JamesCourage says 'play what you like'.
If the PCs have to strip themselves of their heirlooms to tackle a challenge, it will be cause the challenge is something epic and destructive - maybe they're about to dive into a whirlpool of acid on the Elemental Chaos - and not because there's a 5HD monster that they're having trouble handling.
Anyways I dont see it that way, I see it as problem solving. I find PCs these days place too much value on their equipment/items and far less on actual roleplay, which might also be an indication of todays DMing style. Its this eternal safety net - like they are hiding behind their mother's skirts. Item breakage and PC death are the big 'forbidden'.
My PCs have no trouble stripping down to their jocks armed only with a dagger and swimming within the city sewers to get to an underwater door lever. There is nothing epic or destructive about that. They just dont want their clothing getting dirty or their armour wet and cannot imagine themselves swimming underwater with armour and all their equipment.
So if I did throw in a
Rust Monster (which I havent as yet, probably because I have forgotten about it, since its not in my 4E MM) I'd imagine theyd become creative enough to defeat it.
The mage in the party might be interested in the creatures corrosive capabilities and attempt to utilise them in an interesting way in future adventures, if at all possible (I have actually forgotten most details about this creature since we havent come across it since our 2E days).
And with new players, imagine the shock/horror of facing this beast that seems drawn to the fighters/clerics and suddenly begins eating away at their armour/weapons. Its rare to surprise PCs these days, especially the experienced ones. Throwing in the odd beast to mix things up a little adds that little sense of wonder. I'm not saying a
Rust Monster is the only way to do it - but Id welcome it as a nice change, especially since its been over 15 years since we've seen one. They hopefully might not even recognise it at first.
I'm also not a big fan of intelligence checks for GM hints. If you want to give them hints, give them hints. If you don't, don't. What does interposing a die roll add to the game?
True, the roll adds nothing. I feel the same way about Monster Lore, I usually drop the DCs and use their Passive Score. If a player invested enough resources into the knoweldge, or specified as such during downtime - then I generally provide them the information I am comfortable the PCs might have learned.