They're full of crap. I've been in a solo party since about level 69 and now I'm about 81. I grinded on just MDTs and stuff. Of course, people think I'm insane for building my character this way, and they also tell me that my build is that "I'm trying to be a solo priest, which is impossible, and futile." One, it's not, I've seen upper levels train alone at skeles, and other such things.
Second, forget waiting to max SR. If you have really high hp (I'd recommend getting all the equips you can), and or high enough INT to raise your overall Mdef to the point that you don't need MG, you can just use heal. For the purposes of sanity, I'd recommend the latter, as HP mages have many other problems.
Any class IS soloable. You just have to choose the right battle grounds. You can't really solo himes for instance, but you can find other spots that give almost as good experience, with less risk. Such as the dark clown area in the haunted house (which may take some work to get to, if you don't have a key).I'm starting to rethink being a priest then
I thught any class was solo-able
But apparently not
People who say otherwise are typically people who are used to priests healing them, and nothing else, and see priests as worthless if they don't currently have a "crucial" skill (earlier levels it's bless, then later it's HS). When those people are in the party, and try to get you to be support only, I usually leave the party. You were given the attack powers so you can hold your own. But, you are better at healing, if you wanna be a party mage. Just a note, heal is actually stronger than SR.