So as we know Shayzien armour protects the player from Poison splash damage while fighting Lizardman shaman. Shayzien armour is considered melee gear but I find that rather irritating since it doesn't give ranged bonus at all which makes ranged quite innaccurate therefore it seems like its not worth purchasing at all. Since we dont have cannon, ranged is the most efficient way OVER melee to kill Shamans. My suggestion is to give Shayzien armour pieces equal ranged bonus to Red dragonhide pieces. This way it keeps bonusses balanced and makes ranged in close combat a viable option while fighting Shamans, instead of safe spotting them.
Red dhide bonusses which should be applied on Shayzien armour are as followed:
Red Body > Shayzien platebody: +25
Red Chaps > Shayzien Greaves: +14
Red Vambrace > Shayzien Gloves: +10
Since there is no red dhide coif and boots it would be best to give them bonusses equal to snakeskin armour
Shayzien helm: +4
Shayzien boots: +3
Aside of this a few prayer bonus might help too
Second suggestion would be to mount the Shayzien helmet onto Slayer helmet (i) to maintain Shayzien's set effect against poison splash while providing slayer helmets boosts during a Shaman slayer task, yes this is a thing in osrs.