Biochem is only worth having after you rolled armor/synth and artifice for crit'ed relics.
Those crew skills provide you also infinite +28 stat for each augmented slot. More to say they dont need having mentioned skill after craft.
Here comes biochem problem - everyone wants cheap stims, so they come back to it...
Solution is very simple - if you have augmented crafted item you need proper skill to keep it.
Voila - biochem stays with cheap infinite rakata stims only slightly better then ones anyone can use.
Other crafters stay with +56 constant boost in one of chosen stats.
Simple and fair.
edit:
Ok not all that fair - forgot about armstech - something needs to be done about it (maybe it should be able to add augments for offhand and mainhand weapon).