@No:
It made no sense , went against every single plot point the arc had , like the guild meeting this non existant illusion of a guild participated in or illusions acting afraid of being killed when no one else was around etc. , and it's utterly pointless , because there are a milion other ways to make Wendy join in without having to rape all logic and reason .
Is this all you got out of the explanation of the Nirvit?
It made sense but in a way its supposed to be regarded as a twist that the reader wasn't supposed to expect.
An entire Guild being an illusion makes sense since only the guild master was the person required to attend the guild meeting with the other guilds and it explains why the Cait Shelter guild only sent Wendy and Charle anyway.
The old man even refers to himself as a spirit.
http://www.mymangaspot.com/series/Fairy_Tail/164/12
Its not like ghosts don't exist in Fairy Tail and people are able to tell when they are talking to a ghost.
Yeah thats more than enough talk about the OS arc from me. Makes me rage every time I see Erza crying over Gerard.