Sharpmetal is useless,you run out of it after a few kills lol. You don't run out of a champion/death knight with two artifact melee weapons! It is really a shame that dark magic is practically useless. With light one you get all the cool buffs and then just steamroll anything in your path.
7 is the most exploitable game in the series, there's a well in eeofol (I think) that gives free skill points, money, xp, etc. It also dishes out eradicates and kills, but with gm magic resistance you can block the negative effects.
a high end party of dark priests/liches can spit out dozens of dragon breaths and mow down just about anything like it was grass.
There's 0 reason to take melee chars with dark, not just because dark magic is so much better than melee but also because all the mass buffs are on the light side.
dark side - clerics and mages
light side - i usually take 2 heavy hitters (i prefer monks and knights but thieves are good too) + 1 cleric + 1 mage for the light spells and utility (also they hit pretty hard with all the buffs).