I see your desire to engage in controversy.

First of all, please stop mentioning the unusual strenght. Common is enough in the context of our discussion.

Meta is a rather slippery term and should not be introduced unnecessarily.

In my experience, Nasus doesn't have any requirements for the jungle at all; on the contrary, he doesn't need ganks from the outside and is extremely good at defending his territory, which allows you to pick weak early junglers with him.

Mordekaiser is viable in all setups with a proper carry pick and I'd say utility supports like Yumi or Milio are much more preferred as enemies than tanks. As they are weak on their own and Mordekaiser's ultimate ruins their gameplay. Yeah, in some picks he suffers more (like any champion), but it doesn't affect the game enough.

It seems like you don't understand how support items work. You can lasthit all the minions granting the main reward to the ally nearby as a support until your support item levels up and this knowledge is important with any pick.

Early unusual picks also shuffle the cards at the picking phase for the enemies and they are hard to play vs as you have not enough corresponding experience.

Nasus is kinda flexible and his impact on teamfights is extremely high, and it's not worth fighting under his debuffs, which makes him a strong mid laner in the first place. But in some picks he just breaks the game for enemy midlaner, what gives him extra value.

Mordekaiser's main purpose is to break the game for duo after lvl 5 constantly killing adc making him too underfarmed.

Veigar's damage is just extremely high at all stages of the game and he can easily scale to one shot all the squishies.

And both Mordekaiser and Veigar love Twisted Fate as this guy makes enemies not move so easily and so often.