Right now the penalty for these effects is a max of -25% attack for three turns and -30% defense for 3 turns.
With the introduction of legendary and the pre-existing buffs that can be applied for defense and attack, I feel like these weapon mods could use a little love.
If they were buffed to 50% with the same duration I think that would at least give them some consideration for use in battle.
Edit: This is mostly stemming from a want of more variety in viable options for weapon crafting as well as defense teams. In a world of stat buff leaders something like this might force some people to branch out.