Also, no need for warp fields.
There are always enough boyz. If a few die in horrible accidents because of catastrophic weapon malfuction every now and then,...
thta´s just enbtertainment for the rest of the boys until the next scrap.
They just don´t care about the same stuff as we humans.
Official 3rd or 4th edition sourcebook has this phrase about burner boyz hitting their own troops with flamethrowers if no real fighting happens and be all happy about the other guys doing the funny "burny dance" while getting incinerated. It´s all good sport.
Orks are plenty of clever, they just think totally different. And things like dying are not really imporant, unlike stuff as not enough fighting.
Some bosses and warbosses get really scary intellligent. But most of them solve problems with a scream and an axe anyways.