What are your lynch guard armed with?
Lynch guard with warscythes and a cryptek (or equivalent special character), are fantastically tough. Toughness 5, 3+ save and a 4+ Reanimation Protocol are phenomenal. That unit is a great counter assault unit.
All the units you have are useful. I wouldn't use any of those special characters though. If you can get Orikan, he's phenomenal.
I think that most units in the book, besides flayed ones and most of the special characters are quite useful. The Formations are fun if you want to use them (either to supplement another detachment, or included as part of a Decarion). I think that if you are going to use a lot of warriors, ghost arc and Immortals, you want to use a Combined Arms detachment, to get Objective Secured. Once that is done, you can use the formations if they tickle your fancy.
If you have access to it, the Detachment which is included in the Shield of Baal, Exterminatus book (mephrit dynasty?), is really nice and has some fantastic relics and a better warlord trait table.
You're goal should be to shoot the crap out of stuff and then if folks get to close, charge them with wraiths or lychguard. Play for the mission (claim them objectives!) and you should do just fine!