I haven't actually played Rogue or Ninja in this game, but back in NWN I did play a character who, almost always, would run around invisible to avoid unwanted attention, as Invisibility was a particular spell in that game. Â That said, there were a number of ways to counter it, some being spells that last a certain amount of time that directly allow one to see something hidden under Invisibility (aka 'True Seeing', 'See Invisibility', 'Glitterdust' which is kind of like the 'throwing up sand' thing that was mentioned, etc.), or if the person themselves made an 'aggressive' action while under Invisibility, the spell would break, and they'd be out in clear view again. Â Certain proximities also gave it away; there would be a faint in-game sound if someone who was invisible walked by you, and they'd become faintly able to be seen around your character while they were there. Â In addition, the spell would only last certain amounts of time, etc. Â It had lots of counters, and even if none were being taken and my character was around someone being a creeper, I would often emote something nearby someone, and so forth in that vein.
Here in FFXIV, I don't know what countermeasures Hide has; if there are means of detection for  it or not.  But I would play it out most like what other people are saying.  Either ICly or OOCly make it known that you are present, yet hidden.  Potentially emote sounds, traces you've left behind, shifts in the air if someone is really close, and allow the other person to react if they'd notice or not.  Maybe they accidentally run into something, and cause it to move.  Or maybe they can't keep the ability up that long / that well, and people might see strange 'ripples' in the air where the person is, or something (if it's being treated more like Aetherical distortion than flat out hiding and sneaking).  Perhaps it even reacts to certain areas or situations, such as creating a strange 'smear' in the air if the person moves too quickly, or distorts the air around a person if they're in a place of high/low Aetherical potency.  I'd think that the 'restrictions' one can come up with would actually be quite a bit of fun.
But that's just how I'd handle it, and some of that is to say I don't know the exact lore of the action (yet) so I'm not sure if it's all plausible. Still, I wouldn't go about it as 'impervious invisibility' either.
Here in FFXIV, I don't know what countermeasures Hide has; if there are means of detection for  it or not.  But I would play it out most like what other people are saying.  Either ICly or OOCly make it known that you are present, yet hidden.  Potentially emote sounds, traces you've left behind, shifts in the air if someone is really close, and allow the other person to react if they'd notice or not.  Maybe they accidentally run into something, and cause it to move.  Or maybe they can't keep the ability up that long / that well, and people might see strange 'ripples' in the air where the person is, or something (if it's being treated more like Aetherical distortion than flat out hiding and sneaking).  Perhaps it even reacts to certain areas or situations, such as creating a strange 'smear' in the air if the person moves too quickly, or distorts the air around a person if they're in a place of high/low Aetherical potency.  I'd think that the 'restrictions' one can come up with would actually be quite a bit of fun.
But that's just how I'd handle it, and some of that is to say I don't know the exact lore of the action (yet) so I'm not sure if it's all plausible. Still, I wouldn't go about it as 'impervious invisibility' either.