I almost hate to bring this up, since it will undoubtedly bring in complaints of "WotC hates 4e fluff" to yet another thread, but they don't actually call the Raven Queen a god in the UA. She is a "a mysterious
being who rules the Shadowfell from a palace of ice deep within that dread realm." So, in the generic sense, it isn't the case of "gods having warlocks" (unless you are playing in the Points of Light).
I have mixed feelings on the whole "are clerics and warlocks really the same thing", mostly because I think it would have worked out better if paladins and bladelocks had been subclasses of some magical champion class (if you patron type is a celestial, you are a paladin; if it is a fiend, you are a hellblade; etc.).
I echo [MENTION=6801228]Chaosmancer[/MENTION], for warlocks and clerics. While a warlock can use his/her abilities for the group's good, the abilities are all pretty much focused on the warlock's utility and damage. You can build a cleric that is self focused easily enough, but the class contains a lot of things that are as likely to help another party member as the cleric (healing, blessing, removing conditions). So, while the cleric may not be locked into the "leader" role like in 4e, it can support that role.
If they had a lot more celestials and fey, I would say you could fuse the cleric and warlock into some kind of channeller (similar to the magical champion I mentioned before, but at X level, you can channel the spells known by and magical powers of your patron type critter at level Y or lower), but I don't see that as viable currently in 5e.