Do you see much engi in the MAT in the first place? Answer is no.
Holo has a kitten survivability with the nerf it gots and with willbender and harbinger in the meta you realisticly cant do much.
Mechanist is an useless class in this roaming meta.
Scrapper has good+uelist potential + teamfight, good damage, superspeed, access to stability, range, melee, anti projectile, cleanse with elixir gun... I tried to play holo in this meta mostly has a roamer and its big poop.