The new explore system revamps the difficulty but keeps the bugs from the old one. (Yay recycling !)
The stat bonuses from difficulties higher than “normal” in the old system are still being applied to the new one. I.e. if the last explore you did before the patch was on Warlord IV, enemies will get +200% to all stats.
Thankfully you can still change this with casual PVP mode. Just doing one battle on normal will reset the difficulty.
I am unsure whether the gold & souls are affected or not.