So your friend really needs to be able to kill 2 flyrants and 1 tervi. If your friend can do that you will loose synapse and he can mop up your gaunts for an assured tie or win.
The positives your friend has is that he has two helldrakes (baleflamer I hope).
The negatives being; 1)he seems to lack reasonably priced skyfire (only source of this is forgeworld
CSM flyers and
GW fortifications) and 2) lack of oblits which are a great tool kit unit for killing nids.
However not all is lost.
For future reference Be'Lakor is a model and data slate that can be used as an
HQ choice in
CSM armies. He has eternal warrior, is pretty good in melee, and most importantly knows all the telepathy powers
http://www.blacklibrary.com/games-workshop-digital-editions/Dataslate-Belakor.html
He is incredible for a
CSM army but fairly priced.
So the first thing in his list is two helldrakes.
I would then go with 3 one man units of nurgle oblits. This maximized the number of grounding tests he can force on you and keeps him from needing a better
Ld on the oblits. These guys will be very useful for
DS next to your tervi and plasma-ing it to death or if needed
HF-ing your gaunts.
With the selections of units you have stated I would probably go with 3 units of 5 man squads of 2x plasmagun plague marines. They are fearless, Sv3+, and
FnP so they would not be very easy to kill and they can still do decent damage. Throw them in rhino's for some mobility to get where they are needed and waste a turn of your vector strikes. They are also a threat to your
MC once they are grounded as the poisoned attacks makes them decent in
CC and the plasma can kill the
MC pretty quick. Your friend should start his shooting phases trying to ground your flyrants with the combi bolters on the rhinos.
Then I would take a nurgle chaos lord on bike with
LC and
PF for a cheap
HQ to unlock the plague marines and a decent
CC threat. He should never willingly come near your
MC unless they are down to their last wounds and are not a flyrant.
To go with the chaos lord I would take a small unit of nurgle bikers with melta (or if he is specifically writing the list to kill you then plasma). This gives more grounding tests and a fast unit that can contest and in general be where needed.
That should be 2000 pts and if played right he should be able to win the game. It is also a decent overall list with the limitations above.
He really should think about getting an
ADL, firestorm redoubt, or quad lascannon vengeance battery to handle his
AA needs.