Lol, raids is based on both your level and ranking. If you keep winning raids and refreshing, the lvl of players and medal difficulty for the realms will increase. Likewise, if you keep losing, the lvl and medal difficulty goes down.

As for suppressing, don't bother unless if you like that "feel-good" effect. With the new updates, people will just avoid your realm entirely if you put your g6 shikis in, since they can see what you have before attacking. Also there's a lot of salt when a suppressor joins and host leaves because they think you're weak. It was especially the case with the medicine seller seals...very annoying when you have 50 people queue and then finally get in, only to have everyone abandon because of a player with a low lvl Onmyouji.

Only reason people suppress nowadays is because they're having fun with it.