The combination of Dark and Light powers gives the best results, but the LS ultimate power, Force Enlightment, is much better than Crush. As mentioned before, the whole Crush, Crush, Crush, repeat routine is boring and dull. Enlightment turns your character into a tank, but it it lasts for a very short, actually absurdly short time. Also, when mixing there are mot much really useful DS powers- lightning, poison, choke, and probably Scream are the ones I can think of, while all the LS buffs are powerful, yet short lasting. Fear is almost identical to Stasis Field, but Heal is times more powerful and useful compared to Death Field.