If you change the format so it's more eligible, along the lines of something like this would be best
IMHO:
10 Chaos Space Marines - Icon of Slaanesh, 2 Meltaguns - Including Champion with Powerfist - Rhino -265pts
or you can simply look at other peoples posts for ideas on how to present it, you also need to see this (
http://www.dakkadakka.com/dakkaforum/posts/list/281186.page) as you're not allowed to list individual points. If you make it more eligible I'd be happy to provide some more feedback. Anyone providing you with advice should know the stats and rules for the units too so they only add further confusion
IMHO.
Glancing over the list however it looks pretty good. I'd recommend a Power Fist instead of Power Weapon on the Skull Champion, dropping the blastmaster and adding some more goodies to the Terminators (at least 1 powerfist/chain fist is needed to help against tanks/walkers/
MC's and a Heavy Flamer and Combi-weapons are bargains) as basics, but the core of it looks very solid. Rhinos for your units would also work WONDERS!
As for possessed; they can provide very nice parts for conversions, but when it comes to the tabletop they're pretty poor. It's worth bearing in mind however that they do have very good base statistics (albeit at a price) and can form a good counter-assault unit, but that's not really needed too much in a
CSM army.
Plague Marines are significantly tougher than normal marines: Toughness 5,
FNP, Fearless, Blight Grenades and easier access to special weapons are all big bonuses. I must admit, I still prefer
CSM's, but for holding objectives there's very few troops (and thats by and large the main use for troops) better than the Plague Marines.
As I said however, if you'd clean up the format a bit I'd be happy to help. Welcome to Dakka!