You don't have to worry as much about the opponent being stubborn about getting you to half or less either, by the way. Sure, Minior's armored form only has 60/60/60 offensive stats, but if we use our 252 atk and spatk EVs, its atk, spatk and speed reach 480, 438 and 312, respectively. These are not numbers that are usually able to sweep, but the looming threat of a status-immune mixed sweeper getting a second Shell Smash off would give your opponent enough incentive to get you below half. 480 attack, after all, gives it the same attack as Rampardos, and a second Shell Smash would be fine because, while you have a bit less speed (468) than unarmored form with +4 60/60/60, your atk and spatk will become enough to sweep with and you will be immune to burn, paralysis, toxic stall, etc.
Can't ignore Minior. The difference between 1 and 2 Shell Smashes is only one turn, after all.
The point of this post was to quickly dispel "Minior is situational because it relies on the opponent hitting you !!" Yeah, that's optimal, but even without it, you're letting it hit +700 atk/spatk and 468 speed if you try to play that game.