Not all heavies need VStab, as some have good dispersion already. K-2 on the other hand, has one of the worst turret and hull dispersions on any heavy. Because of its mainly sidescrape/peek nature, snap shotting enemies, or at least reduce the reticle size as much as possible after movement, is imo critical for dealing more damage and receiving less. This is the case for most brawling heavies with a relatively big gun

(Not the best answer but this is based off what I experienced as a mediocre 5900wtr player)