Mr Skullhead mentioned on Radio KoL on July 23, 2007 that the Haiku Dungeon was being worked on and revamped, as it was originally created before Asymmetric was formed, by a person who is no longer with the company. On August 29, 2008, the revamp went into effect.
The Most Extreme Haiku Challenges don't appear in any particular order.
References
The various "Haiku Dungeon in the <season>" adventures may allude to most Japanese haiku being about seasons and nature.