Tenniel
First Post
I'm having difficulty understanding how minions interact with the world.
I think how minions interact with the world is different with how they interact with PCs. Having 1 HP is an abstraction (as you noted) and, importantly, an abastrction that assumes the minion is in combat with PCs of a relevant level. This abstraction (and indeed game mechanics in general) are not required to adjudicate events outside the spotlight of the game.
When not part of an encounter minions can go about their lives without fear of dying from mosquito bites. They can have battles with their neighbours and hobble into the infirmary afterwards with a dagger in the thigh and arrow in the shoulder. Now if their neighbours were PCs then either the arrow or the dagger would have slain the creature (such is their fate when encountering heroes). In short, minions interact with the world in a way that you, the DM, dictate to achieve whatever end you desire, be that 'realism', conistency, common-sense, plot or whatever tickles your fancy.
Similarly they could get through the damaging terrain (ouch, ouch) to later be part of the encounter (with deep scratches and their single solitary HP).
HPs represent a lot of things: mass, toughness but also luck and battle experience. It is the fate of a minion to receive a mighty blow in combat from a worthy opponent, this does not mean they are made of tissue paper (refer to a Legion Devil's Fort save)... it means the PCs can easily dispatch these lesser beings with relative ease.
It is possible to set up anomolous situations (e.g. pet cats vs high level minion) with minions, but these can be simply avoided. DnD simulates heroic fiction, which centres on the heroes and their deeds... so omitting the housecat's attacks from the resolution of combat will solve the rules anomaly while maintaing the spirit of the game.