Having Multiple Copies of the Same State - Good or Not?

In my current game, there are a variety of classes which can inflict buffs and debuffs on players and enemies:

- Healer (divine type stuff)

- Mage (mainly debuffs)

- Bard (magical music)

- Psionic (mind control type stuff)

Now, I was thinking that any class which can debuff could, for example, Slow an enemy (or enemies).  But, in-universe, the mechanics of HOW each class does it are completely different.

Why would this matter?  Well, some monsters might be utterly immune to a Psionicist's Slow (i.e. Undead) but affected by a Bard's Slow.  Or, perhaps immune to a Bard's Slow (they are deaf perhaps) but not a Psionicist's Slow.

My goal is to strongly encourage the player to develop party proficiency in multiple classes, rather than overly rely on a single one (i.e. "I'll just use the Bard for debuffs") and add a bit of challenge to the player ("Damnit, this Vampire is ignoring my Psionicist!") without being unreasonable.

Does this sound like a good idea?  Or would it just be frustrating more than interesting as a player? 

I was thinking this becomes important in late-game when a completely new category of opponent (robots, yes in a Middle Ages fantasy world --- justified) comes on the scene...

What do you all think?

Sounds good to me. I was doing the same thing, but with poison effects. As long as you can keep up with them I say go for it.

I'm currently employing that system.  But, it has more to do with Levels of States and Levels of Skills.  I have "Weapon Versions" of states and then I have "Skill Versions" of states.  Monsters will use the Weapon Versions of states so they don't get confusing and it won't clutter up my Items List.

Many of my states are even stackable (I have a Poison that lasts for 5 turns and does 20% HP damage a turn... very deadly... very rare... and the first you start with is a Poison that lasts 10 turns but only does 2% damage.  Doesn't seem like much, but early on it's pretty powerful.  Characters only have maybe 20 HP max to start with.) and can be useful to a player.

One of the other positives is that you can make a variety of equipment that plays around with the states.  Ultimately, states make battle very dynamic because it makes players think about what to equip as well as what to buy to cure the states.  You do have to be careful in how you use them though...  It can be pretty frustrating if the character doesn't understand the difference between two different states like you've mentioned (Slow works fine with one class, but not another).  You should probably provide In-Universe explanations to the player in your game for why that might be the case and why they might want to try the same states with different party members.  It's definitely counter-intuitive from the way most players play (or all... as the opposite behavior has been ingrained in us since RPG inception...  If something doesn't work with one char, it won't work with any other).

I plan to definitely have some characters in-universe explain this different mechanic.  Until some time after that point, all states will connect on all opponent types.  Monsters will use a variety of the state types, depending on what's justified based on their type.  For example:  Most robots won't use Psionic states.  Cyborgs clearly can, but they are also vulnerable to Psionic attacks in return.

I would suggest a variance of each states type. For instance, psionic slow also adds an mp drop rate while bard slow also adds a mute. That would give the player extra incentive to use the differing slow states.