You don't need LK in PvP as a Soul Master. People who say you do clearly don't know what they're talking about. Blessings only work well on Charms, but that's only if they have Mana Reflector on.
My Soul Master has (I haven't played in a long time, so I forget the exact numbers, but) 90k HP/1.7k MA/2xx LK and still does something like 25-35k damage on Mana Reflector. Sure, you could do more if you had more LK, but the difference isn't worth being a glass cannon over.