I recommend you visit our public recruitment discord to ask questions. You’ll get realtime responses, and can talk to a few of our members.
Like all of our requirements, none of them are strict. The reason why I specified “Duo/trio” is because in a duo/trio, there’s more responsibility placed upon each individual to perform well. Anyone can leech in a large shatters/tomb. That doesn’t prove your skill. You should at least be competent in the dungeon you are doing. To answer your question: it’s not that strict, but you can be sure to face an instant kick if you are deemed a burden because of your lack of skill in our shatters/tombs.
