So - Elbow Blades (arm replacements) Knee Spikes (leg replacements) and Hand Talons (Hand replacements) all lower the dps of pawns equipped with good melee weapons.
The reason for this seems to be that they add more attack types to the pool that pawns can choose from resulting in suboptimal situations where your pawn with a Zeushammer will instead opt to swing their Hand Talon. This also applies to Venom Fangs/Talons though.. that's.. a whole different conversation about how useful those are
Power Claws also technically suffer from this though it's typically less pronounced as they do more damage.
(iirc the system is weighted to favor higher damage attacks but not to the exclusion of lower damage one)
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So long story short - Implant weapons on characters with guns = Good
Implant weapons on characters with good melee weapons = Bad.
That's not to say that the implant weapons are entirely useless - They're actually exceptionally cheap limb/hand replacements. A Knee Spike is a considerably better leg than an actual Prosthetic Leg.
Will take a look at this, thanks.