This is not a new idea but I just wanted a separate thread for visibility from SE.
SB has 2 majors balance issues at the moment DRK and Casters.
An elegant way to partially address both would be to give DRK a magic vulnerability debuff (similar to slashing debuff) which would create synergies with Caster comp and re-enforce the magic tank identity.
This would give a unique tool to DRK with real raid benefit.

This could be introduced either by adding our old delirium combo path or (my preferred solution) to Dark Passenger.
Now for it to benefit DRK, BS, DP and all DA enhanced combo enders should become unaspected magical damage.

More than personal dps buff, this would really help bring more identity to the job while bringing synergy with casters that they desperately need.