After looking at the list of basically all grots oast thread, I was inspired to fine tune it a bit, to make it even better, so behold THE GROT TIDE:
Combined Arms Detachment 1:
HQ (200 points):
Big Mek (115pts) Cybork Body, Mega Force Field
Big Mek (85pts) Kustom Force Field
Troops (345 points):
3 units of Gretchin (115pts): 30x Gretchin, 3x Runtherd
Combined Arms Detachment 2:
HQ (190 points):
2x Big Mek (85pts) Kustom Force Field
Troops (230 points):
2 units of Gretchin (115pts): 30x Gretchin, 3x Runtherd
Lord of War (735 points):
Kustom Stompa (735pts) Big Shoota 2x Bursta Kannon, Deth Arsenal, Gaze of Mork, Power Field
Unbound Army (190 points):
2x Big Mek (85pts) Kustom Force Field
1850 points total
The strategy is simple: 150 grots. Use the 5 regular big meks with kustom force field to provide them with a 5++, making them a bit more resilient. Put the big mek with the mega force field in the stompa to give the stompa a 4+ invul save.
Use the Kustom stompa to take out anything big, grots overwhelm the enemy.
Now, I'll admit I'm not an ork player, so I'm not sure if that's the best load out for the stompa, but 2 D guns, one gun that has a 2/11 chance to be D, 3D6 S9 ap3 shots as well as d3 s8 AP3 5“ blast each turn seems pretty good to me.