Hello flaming walnut. Let's take a look at your list.
Your list divides into two elements, three technically if you wish to consider the nob bikers and Wazdakka as part of a warbiker contingent independent of a dreadbash and a speed freak transport army.
Most everything you have taken in terms of upgrades on units appears sound. I would not take grot riggers on a killa kan, except in the extreme case of one for the last one remaining in the squadron. Remember that squadron immobilizations wreck the models until one remains. Same argument goes into battlewagons- add weapons to keep weapons destroyed results turning into immobilization results.
Get rid of 'eavy armor and attack squig for the Big Mek. Give him cybork and maybe something else.
The Nob bikers do not need kombi-anything really. You could mix up a few things such as regular sluggas and choppas along with ammo runts. You want each model to be unique so wound allocation can be maximized. Also, cybork bodies are not a bad upgrade for warbikers (allowing them access to at least a +5 invulnerable save in the event cover or armor gets ignored).
Trukks could use a reinforced ram. That is always good for rerolling terrain rolls.
Now with the list you have, an opponent will probably be drawn to firing at the nob bikers. That is fine, as they can make for a great distraction unit as the rest of the army come up the field. What you want in an ork army is target saturation: the more units and models an opponent has for choosing to hit, the more likely they make mistakes or focus on the wrong threat at the wrong time.
With 9 bikers and Wazdakka, you have a very impressive amount of
CC that can ram into enemy lines within 2 turns. Keep in mind however the amount of points invested into this unit. You spend roughly 500 points into one unit. Don't needlessly sacrifice them unless it is critical to get the rest of your army into position (Nothing says DISTRACTION more than a Nob biker unit).
The Deff Dreads and Killa Kans look unusually out of place with the rest of the army. That can be okay. I would suggest the Dreads be turned into Kans, and the Kans replace all their weaponry with rokkit launchas. This gives the kans more range on their ability to influence kombat, and gives your army much needed ranged fire support (as you have left the Lootas at home).
