I've noticed that the higher level you lion is, the longer and longer it takes for you to level him up. This isn't just because he needs more and more experience for each level, but is mostly because there is no increase in experience gain for higher level lions. Lionesses gain more EXP the higher level they are while hunting; even level 1 lionesses will gain 500EXP if they're sent in a party with some high level lionesses.

I don't really think this system is fair. Males only earn 150-190EXP (190 is the highest experience I've ever gotten from NPC fights, so it's the only one I have to use as an example) from NPC fights in explore. When you lion needs 25,000 or more EXP to level up, it will take roughly 160 fights in order for you to level up. That's if you win all of your fights. If you don't win all those fights it could be closer to 200 fights before you lion will level up.

I think that there should be an increase of EXP for your main males while explore. Maybe each region have a range of EXP you could earn at random. Or set it so that each level earns a certain amount of EXP, on top of the EXP we earn from battles in explore.

Since some NPCs are only found in specific areas, it's safe to assume that they are "high levels" than the NPCs you would find in, for example, the Temperate Savannah, so why am I earning the same amount of EXP fighting a Rocky Hills specific NPC as I do fighting a Temperate Savannah specific NPC?

It just doesn't make sense to have males only earning the same amount of EXP no matter what they're level is.