I really think the guide needs info about how some minions scale differently when you summon more than one. Some minions get full dps when you summon a lot of them. (local immunity minions) Others perform well at one minion, but don't scale well beyond that. (static immunity minions)
You should definitely check to see if Optic Staff and Deadly Sphere Staff perform well as a single summon slot alongside other minions.
Slime Staff, Flinx Staff, and Vampire Frog Staff don't scale well with a high minion count, but they are only viable early game when the minion cap is lower so you won't notice as much. They have the potential to perform slightly better when mixed with other minions.
Hornet staff is rated a bit low, but it does have an advantage of being the only pre-hardmode minion not using immunity frames, so you can use it alongside any piercing weapons in the game without losing dps. Pygmy and xeno both have this advantage as well, which might make them more useful for hybrid builds in some cases.
It is definitely worth mentioning that spider maxes single target dps at exactly 3 minions.
I think the Imp Staff is still bugged, but it can cause player attacks and other minions to miss. It wasn't fixed, but it doesn't block damage for as long as it used to.
If you use local immunity minions alongside piercing magic weapons you might notice that the minion damage has to sync up and deal damage in between ticks of magic piercing damage or melee strikes. This will in most cases negatively impact DPS, especially for minions with a high attack speed.
Summary:
No Immunity:
These minions don't block other weapons from dealing damage and ignore damage from all other weapons. They work great with melee weapons or spammy or long lasting piercing magic weapons. (Rainbow gun, Inferno fork, Crimson Rod, Numbus Rod, etc)
- Hornet Staff
- Pygmy Staff
- Xeno Staff
Local Immunity:
These minions don't block other weapons from dealing damage but can be blocked by melee and piercing weapons. They can be used in large numbers with other minions, but melee weapons or spammy or long lasting piercing magic weapons will temporarily stop them from dealing damage. (Rainbow gun, Inferno fork, Crimson Rod, Nimbus Rod, etc)
- Finch Staff
- Blade Staff
- Sanguine Staff
- Pirate Staff
- Raven Staff
- Tempest Staff
- Terraprisma
Local Immunity (With special scaling):
These give the full listed damage for the first minion slot, but use a damage scaling factor for slots after the first. Unlike summoning another minion, the added damage is not reduced by defense, so these minions may be useful for stacking damage to overcome very high defense enemies. Using many minion slots on these minions usually gives a poor return compared to summoning individual minions.
- Stardust Dragon Staff
- Desert Tiger Staff (+40% damage per slot after the first)
Static Immunity:
These minions don't block other weapons from dealing damage but will block additional minions beyond the first from dealing damage. They can also be blocked by melee and piercing weapons.
- Slime Staff
- Flinx Staff
- Vampire Frog Staff
- Spider Staff (3 immunity slots, one for each spider sprite)
- Optic Staff
- Deadly Sphere Staff
Global Immunity:
This minion blocks and are blocked by everything other than non-piercing projectiles when it comes to dealing damage. I suggest using a projectile weapon with non-piercing ammo with this minion.
I don't know exactly how Stardust Cell Staff works, so I did not place it in any category.