See this is the problem. People look at Ork shooting and think "Just give them more shots, that'll fix it" without realizing that the problem is much greater.
Orks have the lowest average armour saves in the game, with most shooting units having a 6+ save (Tankbustas, Lootas, Flash Gitz, Burnas). That means they die very easily, but the cheapest model in that list is the Burna, and they clock in at 14ppm, which is not a throwaway price.
One way to get protection is Cover. But Cover has become much harder to get, especially for Orks, who have to field big units to mitigate the effects of their low leadership. And even if a unit gets in Cover, it gets +1 to it's armour save....which is a very minor improvement for Orks, taking them up to the same as a Guardman's armour save.
So you could put them in an Open-Topped transport instead, and Orks have 2: the trukk and Battlewagon. But both these options are expensive (Trukk is 82 minimum, Battlewagon 161) and both have a 4+ save and T6 and T7 respectively. 4+ save and less than T8 is bad news for a vehicle in 8th, even if it has an extra wound or two. So you have a fragile, expensive vehicle carrying a fragile, expensive unit. Your opponent will be licking their chops at the thought of that.
Then there's the question of range. Of the shooting units above, only Lootas have good range, at 48". But the rest are 24" or less (Burnas being Flamers, and D3 flamers at that), which means they have to get close to get their shots off, which exposes them to way more firepower. Again, these are expensive, fragile units that must get close to do their job. That would be fine if they packed a devestating punch, but they don't (it takes 18 Tankbustas to kill a Rhino on average).
So that, whilst I could see an occassional use for it, doesn't really fix anything.
