Chant of Vampire will never save you neither in pvp nor while farming.
Best dyes for DC are wit +4 men -4, wit +1 men -1, con +4 str -4
CON is much more useful, because it raises your weight limit which permits you to carry more CP pots and increases your resistance against stun effects.
Also, buffing with a macro is plain stupid. You should buff manually. What are you gonna do if a party member dies without BoN, gets resurrected buffless and you're manaless? Use all buffs? No, you'll have to use the basic ones only.
Besides, there is an order in the way DC buffs, which goes like... Flame Chant, Chant of Evasion (Chant of Movement -Fusion buff that works like Wind Walk and Chant of Agility-, if playing Gracia Final), Chant of Eagle and then the rest. This way you buff the less useful buffs first, and party members have less chances of losing any important buff in case of overbuff. Note that DC usually gets into archer parties.
DC's role in mass pvp is to buff, of course, and sleep enemy's supports or melees as well.
You should always prefer Chant of Earth to Chant of War in pvp.
Finally, you mention absolutely nothing about DC's Fusion Skills.