I'll read the rest of your post later, but wait a second...
Primal Groudon is Fire/Ground. No water moves can hit it = profit, while Groudon uses Solarbeam on everything
Primal Kyogre is pure water and no fire moves can hit it... during rain... wut?
Groudon got a better deal? Maybe?
No, Groudon definitely got a better deal.
ofc, dem water attacks are going to hurt during rain, but still...