Black Box undoubtedly the most used soldier primary for ZF because the health on hit is rather vital for survival, especially when you roam or go solo.
Personally I don't mind if something is changed but most do run Resourceful simply because he has huge health regen. (something like 40 or 50 health over 4 or 5 seconds non-stacking per kill)
It just urges zombies to use a little more coordination. Successful Tar + roar can pin and wreck any player, heavy rushing so they have trouble trying to kill anyone, and just that one spy in the corner waiting for an opportunity can make all the difference.
But then you got larger maps that allow rocket jumping and then they can become nearly impossible to kill unless you manage to camp all the health kits.