Monster Park was changed yeah. The exp and rewards are better, you get guaranteed coins and can buy the Monster Park Extreme potions, but it's limited to 2x/day per account unless you buy reset tickets (from rewards shop or various event shops).
Do normal difficulty for Horntail, Zakum, Hilla if you can. If your range is low, Horntail will take maybe 10-15min but the EXP is good. Krexel takes time too but the EXP is also good. It will get easier at Lv150 if you can use CRA gear.