Horde Orks are doable in a Kan Wall with the cover of a KFF. Start your boyz mobz with no less than 30 shoota boyz per mob, so they can weather the storm, behind a wall of Kans, with some anti armor support from Lootas and some fast elements or other element guarding your flanks and you're good to go. Lootas have an incredible 4 foot radius of fire. Stormboyz range from not competitive to highly competitive depending on who you talk to. Check out a pro Stormboyz opinion
here. Here is an example of how hordy Orks can get.

k:
Mega Horde 3000
HQ: 200
Big Mek: 'Eavy Armour; Cybork Body; Kustom Force Field
Big Mek: 'Eavy Armour; Cybork Body; Kustom Force Field
Elite: 300
Lootas x 10
Lootas x 10
Troops: 1500
Boyz x 30: Nob w/PK&BP; 3 Rokkits
Boyz x 30: Nob w/PK&BP; 3 Rokkits
Boyz x 30: Nob w/PK&BP; 3 Rokkits
Boyz x 30: Nob w/PK&BP; 3 Rokkits
Boyz x 30: Nob w/PK&BP; 3 Rokkits
Boyz x 30: Nob w/PK&BP; 3 Rokkits
Fast Attack: 565
Stormboyz x 20: Nob w/Heavy Armor, PK&BP
Stormboyz x 20: Nob w/PK&BP
Heavy Support: 435
Killer Kans x 3: Rokkits x 3
Killer Kans x 3: Rokkits x 3
Killer Kans x 3: Grotzookas x 3
Total Cost: 3000
That's 251 models total.
OBGOG