I can't make up my mind...

My first scrapper was a DM/Regen his name was Suicide Guy, was pacted with a rad/rad def I think his name was something like Neutron Boy.... Ah, great times. Up until they guted regen and all was lost.... T_T I mustly played him for fun tho, and only played him when my friend was on. then he stopped playing due to bills and junk.... :/

Broken Voltage (War Mace / Electric Armor Brute) Main Toon

I was actually going to STRONGLY suggest against dark melee/regen. Its good for pre-16 soloing. But in issue 16, when you can set to full mobs when soloing, youll DEFINITELY want something that has some good aoe damage. Which against large mobs, dark is just the worst at, especially if you'll be gettign fulcrumed when dual boxing.

Spines, while best at aoe, is personally too lackluster for soloing until you are IOd out for recharge on lunge/ripper/throw spines

As far as secondary goes, i'll agree, if dual boxing with a speed boosting toon, dark armor's end issues will be VASTLY helped by speed boost. Not to mention transfusion helping you not need to use dark regen to begin with.

When soloing, claws is one of the best toons for endurance, besides katana.

My personal suggestion for both soloing, and dual boxing, would easily be something like a katana/dark armor or claws/dark armor. End game with tough/physical perfection in view both are AMAZING combos, that deal great single target, and aoe damage, both solo, and getting great value out of fulcrum shift and everything the fire/kin is going to offer you as well.