I see its best stats being physical attack and defense. If it has 120 defense, it can take a psyshock from M-Garde and live. If it's 95 defense or higher, it takes one from specs sylveon. (This is with 74HP, coz I was too lazy to adjust Ferrothorn's HP stat - I did change the typing tho). This is with no HP or Def investment.
If it was base 90 HP, it'd need base 105 defense to avoid the KO from psyshock from M-Garde.
With max (252 HP, 252 S.Def) investment, it would need more than 90 HP and 90 S.Def to take a Dazzling Gleam from Life Orb Gengar. (Sludge Wave would only do 44-52%

)
Side-note. If it was max investment in HP and Def, then it would only need to be 65 HP / 70 Def to survive Psyshock from M-Garde

At the 90/105 I listed above, it would only take 56-66% from it if max invested.