That said, my experience with Maskwood Nexus has been that there are three types of tribal decks that want to consider it:
1) All Creature tribal (e.g. Tribal Tribal where you specifically want changelings and/or to give all creatures changeling to exploit buffs for more than 1 creature type.
2) Non-Type-Line tribal. This includes things like Saproling.dek, Servo/Thopter.dek, Plant.dek, etc. So if, for example, you wanted a Saproling deck that was also mostly Fungus creatures (but not all) and you wanted the Fungus Lords, Saproling Lords (and maybe some Elf Lords, since more than a few elves make saprolings) you might justify this so that you can give all of your buffs to all of your creatures.
3) Shapeshifter/Theft decks. There are a few tribes like Illusions, Shapeshifter (see below), Vampire, Zombies (some builds - so huge this is easily avoided), etc. that have a strong component of copying and/or stealing opponent creatures. There is often a component of changing/adding the appropriate creature type (Olivia Voldaren, The Scarab God), but that is relatively recent, and there are more that do not amend the type line (Geth, Lord of the Vault, Yasova Dragonclaw).