[The Boz]

Flamer Sentinels for tie-ups, and lots of templates. I don't expect a lot of MCs in a 750 list, but I'd fill out the CCS with 4 Meltas just in case. Maybe even a Vet squad with the same set-up. Chimeras where applicable, and if you have the points. Basically:
CCS: 4x Melta, Chimera (HB/HF, HK Missile) - 155
PCS: 4x Flamer - 50
IS: 2 combined, 2x Flamer - 110
Vet squad: 3x Melta, Chimera (HB/HF, HK Missile) - 165
Punisher: 3x HB - 200 (I have no idea how useful this is)
Sent: Heavy Flamer, HK Missile - 70
The Chimeras are there to offer targets of all armor types, so he can't focus his fire in any effective way.

 

[The Boz]

Tyranids have a metric assload of T4 multiW models. So I theorize that it could be worthwhile. And honestly, I couldn't think of a better way to use those 30 pts. Too low point count for OotF or Astro, and both CCS are mobile, so no MoO...
WARNING! I HAVE NEVER ACTUALLY FACED TYRANIDS! TAKE EVERYTHING I SAY WITH A BUCKET OF SALT!

 

[The Boz]

I'd switch the PF and Chimera around; the melta team should be in a transport, protected. Also, against Tyranids, I'd suggest the Bane Wolf instead of the Hellhound. Wounding T6 MCs on a 2+? Yes, please!