I would go with Great Axe all the way until Guillotine. At 30 you can use axe belt if /WAR and get the same skill as main DRK weapons.
100% this. Shield Break and Armor Break are stupidly good. Shield Break prevents
enemies from using their EVA up skills, most notably Lizard with Secretion and Pugils with Water Shield. At lower levels, the overwhelming majority of parties will not be at the ACC cap, so not only are you making a tremendous difference in your entire party's ability to actually hit the damn mobs, you're downright negating a TP move from working. Armor Break is almost as good once you get in the upper 30s, where melee starts getting some ACC gear. Parties with two GA users combining the two Break WS just melt mobs. Just make sure to use those WS on the pull to maximize your use of TP. Sturmwind is only really worth using once the mobs are T or VT and die too quickly for the -EVA debuff to matter.
If your party uses Dark chains, make sure to burst them with your Drain/Aspir/Absorbs. Elemental nukes are pretty much never worth it unless you have a good INT swap set, are bursting, and are hitting the mob's elemental weakness.
And the number one, most important tip for DRK players: make a damn /p macro to announce when you use Souleater. And make sure to either use it before you get in combat with the mob when you have every cooldown available, OR use it when the mob getting kinda low on health.