This code:

engine = new Engine(false);
engine.States.Add(new SpellState("Power Word: Fortitude", 11, c => !ObjectManager.Me.HaveBuff("Power Word: Fortitude"), true, false));
engine.States.Add(new SpellState("Divine Spirit", 10, c => !ObjectManager.Me.HaveBuff("Divine Spirit"), true, false));
engine.StartEngine(15);

Only the first/highest prioritized SpellState gets evaluated...
No matter what.
How can I make the engine process more than one state of a particular type?

Nevermind.
Found the Engine.StartEngine ignoreIfAlreadyLaunched parameter :)