Here's my thoughts:
http://40kunorthodoxy.blogspot.com/2014/11/haemonculus-coven-book.html
and a Battle Report a guy did with me:
http://40kunorthodoxy.blogspot.com/2014/12/haemonculus-coven-vs-astra-militarum.html
My impressions over time:
You have to addres the
AV 12 issue. Dreadnoughts are highly dangerous to your Dark hide. Storm Raven Blood Angels will laugh at your army when they hit the ground. Might kill you to do it but putting Scissor hands on the unit leaders is probably going to have to happen in a PURE Coven list.
Grotesques are boss. You're absolutely doing it right if you put them in a Raider with a Haemonculus. I think an Agonizer is a big deal for them. Aethersails for the win.
Corpsthief Claw with its Scout rule is a big deal. Getting Victory Points for smashing little dudes? Big bonus. Haywires are pretty cool on them. I am a fan. here again: watch out for those multi-Dreadnought units and if they ever get to you, SMASH all the way. Don't bother with normal attacks. You need to destroy those stinkers and reduce their number of attacks as fast as possible.
Ossefactor is probably not a bad way to go on the Wracks. I have tried all the weapons they have access to and the only ones I truly recommnd is the ossefactor and Hex Rifle even though honestly, going minimalist with them is just as good an idea. they actually do have some nice punch with Poison and three attacks on the charge.