Priest training areas

You can put 1 point in shining ray (then max hs) and go to CDs (this map:https://maplelegends.com/lib/map?id=742010203 and here is how to get to Taiwan https://forum.maplelegends.com/index.php?threads/guide-how-to-get-to.18926/)
Be prepared to burn some potions, but the exp makes it worth it.
If you find a DK partner you can train on CDs by healing him while he uses roar.

 

I think this is the best suggestion, or MPQ if you have patience

 

gs2 for level 72 priest is still super fast man
you feel it slow when you are level 90 priest
cd is fast but burn potion and esay die

 

There's still value in grinding gs2, especially considering it costs zero pots to do so, the profit is quite good at that level thanks to gacha.

But it does get quite tiring spending that much time in one map.

CDs with a DK is a great option.

You could also just shoot out a smega to find any party to play with. Just any group grinding together is going to make decent exp.

Additionally, now that you have Shining Ray, it's a good chance to take a break from ghost ship and do some card farming for a change of pace.

 

I think lv 6x-8x and 11x-120 are perhaps the most tedious, but...., every character will have some "hell levels"