Gaining levels is very annoying at some point. After you reach 170 level and you haven’t grind much also you used all of your cards. You get to the point when getting 1 level takes you about 5 hours of very annoying farm. Maps 170+ has very little mob density and respawn time is way too long. It’s impossible to get level 185 with just questing as maps gain level advantage way too fast and mobs are getting too strong for you, even having token activated
My suggestion is to easy up the leveling. There is few ways to do it: increase exp rate, increase resp time/density of the mobs, make experience card drop not 0,1% but something around 1%.
Skiping Demon Prison grind from 150 to 170 puts you at very bad place. Game is being less enjoyable as people struggling to farm experience. Player base will increase greatly after converting to F2P and leveling will be even less enjoyable.
PS: What I liked in Ragnarok Online is that all mobs give you experience regardless their location or their lvl, they always give the same amount of experience so people are not limited to few maps that they can not like, but they can more around the world killing everything and still get experience. I would love to see it in ToS one day.