Primal Kyogre was really dissapointing at first to me.
But when you think about it, it has a few things going its way
1.It can run a calm mind set to good use
2.In doubles,compared to groudon it gets origin pulse that gets the primordial sea boost which precipice blades does not from desolute land.
3.Primal Kyogre can be used on trick room teams also where it fairs quite well.
4.Can serve as support to a plethora of rain pokemon and others including scizor and ferrothorn while groudon generally teams up with cholorophyll pokes which have there fire weakness compounded due to sun.