I'd like to start off by saying Paradancer Groudon doesnt seem to be too useful. I have rarely ever seen Thunder Wave be useful when using Paradancer. Once, people see you firing off a Thunder Wave, the usefulness substantially reduces. Secondly, like Poppy said nothing of note to Reshiram ever switches into Groudon such as a Palkia or Offensive Kyogre (not monoatttacker that is). Therefore I would like to propose this:
Groudon @ Life Orb
EVs: 124 HP / 252 Atk / 136 Spe
Adamant Nature (+Atk, -SAtk)
- Rock Polish
- Fire Punch / Swords Dance
- Stone Edge
Good ol' Rock Polish Groudon. This thing is phenomenal as a offensive lead to beat Dialga as well as a lategame cleaner. I play it like the normal RP Groudon except I use this as a lead several times especially against Dialga. You could easily go for even higher Speed investment but this seems good enough. Dialga flat out dies to a Earthquake and a lot of other mons take a crap lot of damage. Fire Punch is up there to nail any Ferrothorn or Skarmory but if you're feeling adventurous use Double Dance as well. We don't really care about Ferrothorn. A simple prediction and a switch to Reshiram is enough to turn the tables and bag a Flame Charge speed boost.
After a Rock Polish you outspeed everthing up to Scarf Garchomp which is quite rare but nevertheless a threat. The best thing is that Reshiram and Groudon have superb functional synergy especially these two sets. This Groudon can also take a hit from +2 Extreme Killer if the need be so its not totally useless on the defensive side. About, the OP, this is actually a compromise between Shrang and Poppy's Groudon set. It can boost its stats and sweep if needed but also has a lot of offensive pressure from turn 1.