Nope, it's a 2HKO at best.
Superpower is still the way to go for Blissey, plus you won't have to risk missing against Darkrai and Dialga.
Life Orb or Focus Strip are good items for it.
Superpower/Shadow Ball/Grass Knot (for both Kyogre and Groudon) /Ice Beam offers good coverage against other ubers.