Most armor should need to be worn as a set to acquire the attribute bonuses. Silent Legion for example… it was nerfed because mixing and matching made each piece OP, however it SHOULD have +3 to each attribute, but require the entire set being equipped to grant the full points, without the full set it should be only +2 as it currently is per piece.
Silent Legion is useless as it currently stands, so is all the other hybrid armor. Most good builds have at least one attribute above 40. A +9 bonus to your highest single attribute leaves you with a tremendous amount of leftover points to put in your minor stats, since you would only need 31 raw, or less if you’re basing it around other buffs, completely outweighing any hybrid set.
This obviously would be circumstantial, legendary armor such as Helm of the Brute would still give +3 strength.