Never got into MGS games (and yet beat the first 3). SotC is about puzzles and is really not as complicated as it looks. God Hand is the same as any hardcore action game, in that the bosses often will defeat you repeatedly, but are definitely doable. Might want to mess with your moveset a bit to see if that helps, and remember, landing enough normals on a boss will stun them and let you do a QTE of sorts for significant damage.
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"God Hand is the ultimate expression of the joy of humanity, specifically the punching part of the joy of humanity."-Shigeru Miyamoto