Take off the individual points costs...
IMO, don't mix weapons on the Havocs, go with 4 ML's or 4 HB's... for vs. IG, 4 ML's for anti-tank.
Raptors, GET THAT SECOND SPECIAL WEAPON !!!! it's a waste if you don't, major waste. IMO, powerfist or claws on the champ, let the power weapon be the Sorceror which will most likely be attached to them.
HQ- Meh.. a lash sor...
plaguemarines are ok as troops, remember you don't need 7 man squads in them anymore for benifits.
___________________ _____________-after the PM.
You should trust yourself. THe army you use is your army... what you say go's...
We are here to provide input, some are good others are bad, it's ultimately up to you.
As for fights against IG.
There's really no 'great strategies'... it mostly deals with target priority, managing LoS and firing lanes, and usually getting into Close combat with IG.
IG themselves have counters to CC so watch out for Rough riders. Cover is important to both sides. Bolters are decent versus his troops... um... target 'HQ' units, their leadership bubbles can get annoying. SIde armor shots on vehicles are 'gold'.
Don't get carried away with lashing stuff... you might charge something wipe them out... and then are left out in the open for something to shoot you or worse rapid fire... do not underestimate a bucketload of dice thrown at you.
Etc... most strategies are very simple... but applying them or even just remembering them in the 'heat of the fight' can be hard, calm and collected.
My 2 Cents.