The thing is, there is no barrier to entry. No one is exluded from joining an event, only starting it.
If there were no cost and any guild size could do it...there would be events all over the place all the time. I really don't see this as a barrier, though. A guild of 5 doing events together can get this much influence quickly, let alone what you could do if you did a few dungeon paths for money and turned that into influence. 5 people can easily get enough gold in 1 hour to get 10k influence needed for the Art of War 5 upgrade, for example.
I think a lot of people in that thread are upset because they aren't understanding how easy this is.