I think 1000 points is too small to field Ogryn, they take up a huge amount of points which you really want to be spending on some more shooty-ness.
Your right, they have proved to be more amusing than useful. On one occasion they killed around 300pts of nids before being charged by 3 separate units at once which still didn't kill them all until they failed there leadership test and ran. I'll save them for a 2k list.
I wouldn't take the Mortars - you already have lots of anti-infantry shooting from your infantry squads.
Mortars have probably got to be hands down my favorite
IG unit, there cheap and extremely annoying. There has yet to be a game were they haven't killed at least there point value worth of enemy models or held up something useful due to pinning.
You should take Commissar's in one squad in each platoon - they are vital for keeping squads fighting, better at receiving orders and denying killpoints with combined squads.
Your right once again, I actually originally had one or so in the list but took them out list minute.
More Meltaguns, Lascannons, Power Weapons with up to 40 Stubborn Infantry and Rough Riders for counter-attacking from Reserves.
I'm not sure about more Lascannons since most of the people I play against don't have many vehicles but I agree with everything else.
I will post a revised list soon.