First of all, he didn't lose....Orks never loose.
Ork Solution to every problem
Step 1 - Moar Boyz
If the problem is solved, go to step 3, if not go to step 2
Step 2 - Moar Lootas
If the problem is solved, go to step 3, if not go to step 1
Step 3 - Waaaaaaaaaaghhhhhh!!!!!!
Grey Knights are tough, but other armies are becoming tougher for us because the cost curve is getting bent down. Heck when da boyz get a new dex, I am sure that I will need 3k of orcs just to make a 1.5k Army.
Shock Attack Guns are good for Paladins (with the right rolls). Lots of Lootas and cheap tasty kannons protected by t7 grots. I personally have given up on regular Nobz with PK's cause they just die.
It is a sucky expensive unit (worst in the dex), but Flashy Gitz (with the right rolls) could put a hurting on Paladins. Another thing to try is a DeffBurna Wagon (deffrolla battlewagon with a mob of burnas and meks). Lots of flame templates and the meks have plasma guns and can repair damage on the wagon.
And don't forget, Old Zogwort can turn Matt Ward...I mean Draigo into a newt...ummm...squig.