Let's see...
-warboss needs more punch. i would kit him with mega armour, attack squig and cybork body, with total of 125 points.
-you need more nobz. one of the bright side of them is that you can make them to a deathstar(!!). start from six and, in time, reach to the optimal ten.
-ork shoota boyz are very versatile, cabaple of both shooting and close-combating efficiently. i would recommend to use them, with big shootas. don't use rokkits, 'cause shoota boyz are meant to shoot infantry. also you've got to get them more, and when i say more i mean M-O-R-E
-grots are good meat shields and objective holders, but that's about that. you have to have a lot of them
-trukks are meant to be cheap. i kit them with red paint job, reinforced ram and rokkit. rokkit because it becomes a threat to the opponent's forces.
-combine stormboyz to one unit. units of 5 get blasted away in an instant.
-use buggies as a squad of three, with t-l rokkit launcha.
-i use deffkoptas the same way as you do
-looted wagons have boomguns, strongest ordnance weapons available to the orks. use 'em.
if i had to put it bluntly, i would do like this:
Warboss
-mega ramour
-attack squig
-cybork body
=125p.
10 Nobz
-3 big choppa
-3 power klaw
-3 shoota/skorcha
-10 'eavy armour
-2 bosspole
-Waaagh! Banner
--Painboy
--10 cybork bodies
=460p.
30 Ork Shoota Boyz
-3 big shoota
--Nob
--power klaw
=230p.
29 Gretchin
-2 runtherd
=107p.
Trukk
-rokkit launcha
-red paint job
-reinforced ram
=50p.
20 Stormboyz
--Nob
--power klaw
--'eavy armour
--bosspole
=285p.
3 Warbuggies
-3 twin-linked rokkit launcha
-3 red paint job
-3 wartrakk
=135p.
3 Deffkoptas
-3 t-l rokkit launcha
-3 buzzsaw
=210p.
Looted Wagon
-boomgun
-2 big shoota
-'ard case
=125p.
-------------
=1727p.
yeah, sorry. this one here became abit more than 1k but this is what i would suggest with those troops you're holding. and getting these shouldn't prove to be too costly, i think