Not too much harder. We're already used to having to rejoin after dying, and having our mons 1 hit by undodgable Charged Moves.
Even though Groudon is easy to beat, my team (as well as everyone elses since I'm a pretty high level) usually gets wiped once. The timer is pretty fair since Exeggcutors and Gyarados have pretty high attack, and Clear weather makes the fight more interesting always.
Best part is everyone has high level Exeggcutors following the Weather Update.