Are there any game breaking consequences in this house rule for multiclass spell slots?

Question

Follow up to this question.

So, as stated in that question, I feel that it is quite weird that a 3rd level paladin + 2nd level Ranger is not equivalent to a 5th level Half-caster (such as a 5th level Paladin), but weaker (being equivalent to a 4th level Paladin).

With that in mind, I intend to use the following multiclassing house-rule for determining the spell slots:

• Sum the levels of the half-casters first. So, in the example, 3 + 2 = 5.
• Divide by two. (Divide by three for Arcane Fighter/Rogue - both after summing them together as well).
• Round it to nearest integer, rounding .5 up¹.

Obviously, this only applies to classes that actually have the spellcasting feature, i.e., the Paladin and Ranger should be at least 2nd level, and the Fighter or Rogue should be at least 3rd level.

Such an idea is not novel and already appears in the Artificer, which is explicitly described as having its half-caster levels being rounded up.

From my understanding, this house-rule will mirror the behavior of single class spellcasting of half-casters and third-casters more closely (not entirely - rounding up would mirror it perfectly). Is there any weird edge case that I am missing that would make this house-rule imbalanced in any way?

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¹ The only reason I round to nearest integer rather than directly rounding up is that a 4th level Arcane Fighter would contribute as much to the spellcasting as a 4th level half-caster. Although this is what happens in single class, my gut feeling was that this would make dipping 4 levels in a Fighter, for example, be considerably stronger than before, since specifically 4th level also includes an ASI.

Answer 1

It might not be doing exactly what you want

It could encourage a smite-obsessed Paladin to take a 1 level dip in a full caster

You want a Paladin 3 / Ranger 2 to have as many spell slots as a paladin 5, which is what your solution does, but it also has the (perhaps unintended) side-effect of buffing the following combination:

Half caster at an uneven level + any other full caster

A Paladin 3 / Sorcerer 3 under normal rules has 4 first and 3 second level spell slots, being equal to a 4th level spell caster.

Under your new house rules, I'd be summing up all my half casters (3), dividing by 2 (1.5), rounding up, leading to me being equal to a 5th level spellcaster and having access to two third level spellslots.

This might mean that it suddenly becomes a lot more viable to take a single level in a pure caster if you end up at an uneven level of Paladin in your build anyway, your new rounding will result in more spell slots for smiting that way.

Instead, I'd simply change your houserule to read as following:

If you have multiclassed as multiple half-casters such as combining a Paladin and a Ranger, but do not have any other spellcasting classes, you can add the class levels together and gain spell slots as if all those levels were in a single half-caster class. For example, a third level Ranger / second level Paladin will gain spell slots as if they were a fifth level Ranger or Paladin. If you also take levels in a full spellcaster, default back to the normal spellcasting multiclass rules to see how many spellslots you get.

It does exactly what you want (buff half-class combos), without making it easier to cheese out extra spell slots in your paladin build by taking a full caster class. This will be unlikely to break the game in any real way, by multiclassing from paladin into ranger, you are likely losing more than you are gaining from your extra spellslots.

Answer 2

The only thing I can imagine is the same things that are explained in the answers to this question.

It's unlikely to generate a mechanical imbalance, however it reduces the cost of multiclassing. Whether that is an issue depends heavily on your table.

I can't see any reason why this would be too powerful; after all the spellcasting is (by definition) a secondary concern for these characters and you're reducing the power of their spellcasting already, just by being multiclassed.

The odds of this showing up at your table are minimal and the mechanical gains of an extra spell slot per day are totally and completely overshadowed by not having Extra Attack (which most of these half-caster classes get and rely on to deal their main damage)

I don't think there's an edge case you are missing here.

Answer 3

Do what you feel is right for your players.

That said, you may want to consider the source of the caster’s power and weigh it against the complexity of the rule.

Wizards are gaining power through arcane study. Warlocks through connection to a darker power. Sorcerers have it in their blood. Clerics and Paladins draw from the divine. Etc.

Obviously, a Cleric/Paladin split may have an opportunity to achieve a deeper connection to one’s patron. A Sorcerer who takes a few levels as a Wizard may learn a deeper understanding of arcane power and benefit.

I’m sure through some creativity one could come up with several possible synergies for spell casting multi-class combinations which build on each other over time leaving a complex, nearly unworkable system to maintain.

To simplify all this down, have you considered offering extra spells slots and/or ability as an optional feat for the multi-class caster?

Answer 4

You are still going to have the same problem.

Ranger 2 Paladin 3 will have 2 second level slots, but no second level spells. Your house rule doesn't suggest a way to resolve this problem. Having a level 2 spell slots but no level 2 slots is not as powerful to having slots and spells.

It gets worse the higher the levels get. Paladin 10 Ranger 10 only has 3rd level spells, but has 4th and 5th level slots. While these can be used to up cast, that doesn't sound fun to me.