The proc on Soulbinder for example is a DOT lifetap. Thus if it procs twice in a short span of time it limits it's own damage potential. Intelligence is probably the most important stat to increase at startup unless you have deficeincies in other stats. Intelligence equals mana. While you may not care about it much early on it will make a difference later in your shadowknights life.
Intelligence is also harder to increase without trading armor class.
There are many strenght items which feature high armor class. There are far fewer items which increase intelligence. When it comes down to armor class or stats I would choose armor class in most cases unless they give a good amount of intelligence or mana. Wisdom or Charisma are more or less throw in stats for a shadowknight. I wouldn't ever spend any points inreasing either of these.