Description of the ability:
The psyker has learned how to block the messages of the target’s senses. The psyker makes an Opposed Willpower Test against the target. If he succeeds, the target is struck deaf, blind, and is unable to scent or taste for as long as the psyker maintains the power plus 1d5 rounds. This power can also be used as a crude form of effective ‘invisibility’ allowing the psyker to pass unnoticed to sight or sound. The psyker selects a number of targets equal to his Willpower Bonus and selects which single sense he wishes to suppress. This must be the same sense for each target. Each target must make an Opposed Willpower Test. Those that fail notice nothing out of the ordinary, and the sensory information is successfully masked by the psyker until he stops maintaining the power.
Blinded penalties are well described:
A blind character automatically fails all tests based on vision and automatically fails all Ballistic Skill Tests. He also suffers a –30 penalty to Weapon Skill Tests andmost other tests that ordinarily benefit from vision.
As well as deafened penalties:
The character cannot hear at all, or at least not well enough to communicate with others. Until the character recovers or has his disability repaired, he automatically fails any Skill or Characteristic Test that relies on hearing. Apart from having trouble communicating with his fellow Explorers, the GM is free to decide what effects a deaf character will have on the game.
However, my players argued that when you are blinded you rely on hearing to make a task. For instance, a blinded explorer could still shoot in the general direction where fighting noises come. Hence, they say that the penalties of being both blinded and deafened should be way higher, and even incapacitating.
What penalties should I apply? Double the deafenead penalty? Make affected characters as good as incapacitated?
EDIT: Should I consider penalties based on the lack of smell and taste too? Maybe on animal NPCs?