I’ll get right to the point: Warlocks shouldn’t exist in 5e
I know, I know - put the pitchfork down for just a moment.
It’s not that Warlock’s aren’t fun (they are).
It’s not that they’re game breaking (they aren’t).
It’s not that the basic concept is bad (blood pacts and oaths with ancient beings are a staple of the fantasy genre, and they make for fantastic storytelling).
And it’s also not t that they’re particularly broken mechanically (a few talks with your players or creative combat design can mitigate the ole Eldritch Blast issue).
No - Warlocks shouldn’t exist, at least not how they are built and played in 5e, because they are fundamentally unfair to the other classes.
Let me explain.
Baby’s First Blood Pact (Warlocks in 3.5e)
To begin with, it helps to take a look at the origins of the warlock class. It first showed up as a class in 3.5e, designed specifically to be able to outpower any other spellcaster of the same level. It’s concept is simple: a spellcaster that gains their powers through a pact with a powerful entity.
So, an arcane spellcaster whose magic is received due to a body-or-soul connection? Allowing magic power to be cast without a spellbook and intensive arcane study? So...a sorcerer? 5e even suggests “you are favored by an Archfey” as a backstory for sorcerers in the Player's Handbook - that’s almost exactly a Pact of the Archfey Warlock right there.
This isn’t much of a problem in 3.5e, unless you’re a particular stickler for worldbuilding. There, the playstyle and build of each class varies - you build up to a concept with the features that you choose, which in turn adapt the method in which you can best play your character. For spellcasters, this is usually in the building of your spell list; for rogues and rangers, it’s in the allocation of skill points; for fighters, it's in feats, which they get broad choice from instead of pre-set class features every time they level up.
3e Warlocks, boiled down, are spellcasters that build and play like fighters.
Instead of customizing your character by what spells they can cast, with casting and play style determined by your class, Warlocks choose Invocations, which are essentially magical feats, and develop their play style in that way.
These invocations are slightly overpowered, to allow them to outclass their spellcasting peers, but it fits within the play system of the game overall.
Thus, I haven’t much problem with Warlocks themselves, just 5e’s implementation of them.
Playing a Warlock Today (Warlocks in 5e)
It’s pretty obvious to anyone who even takes a cursory glance at both editions, but 3/3.5e and 5e play very differently from each other. I’ve met plenty of fans who reduce it to “5e cuts down on the math and fiddly modifiers”, but 5e reduces more than that, really.
5e streamlines the whole play of the game. Each class plays exactly the same as every other - you choose your class, and then your subclass, and you’re locked in. Even multiclassing isn’t terribly useful. It’s a simple path to follow, with minimal customization. There are 5 choices maximum: race, subrace, background, class, subclass. That’s it.
It plays more like a standard rpg video game than most other tabletops. This isn’t necessarily a bad thing, but it does sort of negate the real differences between sorcerers and warlocks.
But that begs the question - in a game system where class differences are primarily found through creative setup, rather than playstyle, how do you handle 2 classes that are thematically connected, but differentiated by playstyle alone?
5e’s answer was that it...doesn’t.
Not really, anyway. They went ahead and built two different classes, for no perceivable reason as far as I can tell. But to make them two separate classes, they had to alter the play style and build between them.
Instead of the normal spell-slots-and-levels setup of other classes, Warlocks get a small number of slots and always cast at the highest spell level, limiting their casting capacity. In exchange, they get more powerful cantrips, spells, and even a variety of martial options, both in the main class features or selectable through Invocations.
Oh, those Invocations.
I’ll get to them, just you wait.
Pacts, Patrons, and Invocations (oh, my)
So, if Warlocks are essentially Sorcerers, why are they so much more popular to play? Surely, they’re not so much more powerful that you’d be a fool not to choose Eldritch magic over Wild?
The answer is that they’re not more powerful necessarily, nor are they inherently more interesting. But here’s the thing:
As I see many people putting it online, they functionally get two subclasses: Pact and Patron. Plus, they get invocations, which the player gets to choose and change out as they level up, on top of the spells which are inherently customizable.
If it were just the two subclasses, I wouldn’t have so much of a problem. After all, Pacts don’t really have that many features built into them. But Invocations are a different story - the fact that you get to choose which ones you get means that you can essentially select and change your class features. It’s another whole layer of choice and options for difference playstyles, customizability that other classes can only dream of.
This makes them easily the most customizable class in the game.
It makes them the only custom-building class in the game.
And it turns out, while many players wax rhapsodic about the streamlined simplicity of 5e - a lot of them really like the increased customization that 3.5e offers, even if they don’t realize that 3.5e offers it. And that makes Warlocks, the class most similarly built to 3.5e classes, very appealing.
Yes, Artificers also have Infusions which the player can select and change. I don’t have any proof of this, but I’m fairly sure that Infusions were given to them because WotC saw just how popular Warlocks are, and wanted to mimic it. That, or they realized that it doesn’t make any sense to have only one class that allows such a thing, and designed it so that Warlocks aren’t entirely alone anymore.
A Hexed Class (Why Homebrew Can’t Fix the Warlock Problem)
Why shouldn’t they exist then, if they’re more customizable?
People like them - heck, I like them. I started playing DND with 3e, and still favor it in terms of actual play style. Warlocks build more like a 3e class, what’s the problem with that?
The problem isn’t that Warlocks allow for more customization. It isn’t that they’re more appealing to players because of it.
The problem is that only Warlocks are built like this.
It’s unbalanced, and shoddy game design to have a singular class have more options and build differently than all the rest. Especially when other classes (particularly martial ones) were stripped of almost any player-selection options in the same streamlining process.
If Warlocks are built with Invocations, Fighters should have their Feats, Rogues should have their Skill Points (not just Expertise), Rangers should have their Animal Companion Tricks.
But the fact is, they don’t.
And while it would be more fun to simply add in those missing customization options for other classes (I’m usually a believer in improving the disadvantaged rather than disadvantaging the already improved), it’s not possible while still keeping that streamlined simplicity that 5e is so praised for - that it runs on.
It’s entirely impossible for Fighters and Rogues without redoing the former's entire class build, and the entire 5e skill system for the latter.
The simplicity isn’t bad! Neither is the customization! But you have to pick one, Wizards of the Coast.
You can’t have your spells and cast them too.