Like I said, if any decent player spots a mine, they’re gonna destroy it whether it takes more than one shot or not. And because of the very nature of them being traps, when they’re used as such they generally won’t be near other enemies to make a longer time-to-destroy even matter. Giving things like the drone or medstation high HP means enemies can shoot at you while you try to destroy it, but that doesn’t work for something that’s rarely used near enemies for the context you’re talking about.
Besides explosives, random lucky shots also aren’t an issue for such a small deployable. It doesn’t really buff them so much as it makes them more annoying, and there are better ways to buff mines besides HP.
Not to mention taking multiple shots to destroy it means it would be harder to reliably kill an enemy with their own mine, which is a feature that exists to punish a bad proxy.
You just have to be smart about where you place your mines, but they can still be very effective traps. She’s not supposed to be stoker, and buffing her to be better in area denial would just unnecessarily slow down the game even more