I whispered a GM ingame when I spotted a botter. He apparently went in hide to spectate/check him and banned him (was looting drops, the botter wasn't even picking, then he suddenly disappeared and got aggro, died. fml). He sent me a whisper to thanks me just after that, stating he was banned.
Still, they do care.
I think it's better to tell them when they're ingame, so they can live check/spectate.Yet I do believe there are more than 300 botters.