VV/RR/GH for parties. I replace GH with Apocalypse for NMs and events. I don't really solo in abyssea so can't help you there.

For merits, distribute between Scythe and Great Sword skill, giving most to your preference or keep it even, whatever floats your boat. Max out Desperate Blows and Last Resort Recast. The rest is really your choice, but I have at least 3 in Muted Soul.

From there, just build those STR, HP/MP and Critical Hit to your tatse, if not maxed out, then stick the rest where you feel comfortable. Really, though, the absolute choice to make is Desperate Blows 5/5 and LR Recast 5/5. Just be wary of what you raise/lower in categories other than DRK since they affect all jobs, which is why raising stats, HP/MP and Crits should be your decision. Since I am a DRK main, I capped STR and Crit rate and Put a majority of my points into HP with only a couple in MP.

This is just a general run-down. Any specific questions you have?