Actually, Domi buffs are for mages mostly. DC is better for fighters.
Also, DC replaces other classes, he doesn't get replaced. He is much better than a pp. He can buff a whole pt much faster, and doesn't lack anything really special. Just some resists.
Bless the body can be replaced by a Cardinal's Body of Avatar.
Bless the soul by Feline Queen - Bless the Soul.
Berserker spirit is rarely used in pvp. Plus, it can be replaced by Dominator's Rage of Pa'agrio.
I strongly believe that pp and se are 2 of the most useless classes, when it comes mass pvp.
Though, it's a fact that all DC does during mass pvp is buff, sleep enemies or res healers if bd/sws can't. Unlike Domi that can really make a huge difference in the final result of a fight. Seals, cp heal, Pa'grio's Fist and of course FoI...