Mecheon
Sacabambaspis
While the Cleric and Warlock both have the shared things of "borrowed power-sources" and, domains/patrons, they do not mechanically merge together into a single class in the slightest. And as long as there's that mechanical distinction between classes, they'll remain distinctWhich is another reason why IMO the idea of the warlock could easily be a subclass of Cleric. The three pacts (chain, blade, and tome) could be akin to the different animals of the totem warrior for barbarian or the options for hunter for rangers.
Especially all this talk of wanting to merge druids. Thanks to Warcraft, we are in a time where the Cleric class is at more risk of being dropped than one of the Big Classes that people know and replicate elsewhere. Druids are not going to just be sub-classed into Cleric any time soon