But with your thinking they would have all had to have very high Dex especially when I has a Wisdom of 20.
The roll for See Invisibility is not affected by any stats, be it Perception, levels or anything. It is a flat DC 13 Dex save.
Which is kind of low. Especially if you consider late game Dex based characters will be having +4 proficiency and like +4-5 Dex modifier for +8-9 on their rolls (Meaning they have to roll a 3 or less to fail it)
So even if it isn't bugged, it's pretty terrible...
