hey saigo, i'm just watching the rep.
Here are some things i remarked yet:
- You invested too much Req in your BM-Sluggasquad!
- You haven't been able to make much pressure at the beginning which is imo very important for ork (atleast of most maps)
- take 'your' outer left LP much earlyer!
- I am now at 10:40... you have 700/300...don't let your eco float!!! You could have build a 5th Waaghbanner and go for MAN's or go for Vehicles (as David said, fast Vehicles is imo the best thing you can do, cause NObs will lose to plasmarines + plasscouts in 90% of all cases)
gonna edit this, when i finished watching the rep 
EDIT: kk finished the rep.
As i see, you went for both, MAN's and Vehicles^^
Killa Kanz aren't worth their money in most cases imo. They're great for raping your ennemies base but they do shit against large inf-squads.
And you really had too much eco floating...when you see that you have much eco and perhaps don't know what to build, ALWAYS up your LP's to LP2's!! It's +6 income for each LP2 and eco is really important in DoW!
Apart from that I don't think that you surely would have won the game if you killed his FC early on, even it was a nice move though! 
But it's hard to surround heroes, cause of their abilities to throw away your units.
All in all i think that you are doing really good, it's only some minor things you have to improve, so go on and play! ;P