Indeed, you MUST see what you shoot at. Period. This is WHFB, not 40K. In 40K, that is more close to modern warfare, the concept of indirect fire exist. However, indirect fire was not a concept back in time and the Warhammer fantasy rules reflect that!
As for screening your harder troops with lighter or expendable ones, THAT has been done since the dawn of time almost. It is standard tactics. And for greenskins it is a fluff tactic.
Also, it is called attacking in waves, another well-known tactic.
It is also about sense. 6th ed. had restrictions on what you could fire at based on the proximity to the target, just like 4th ed 40K. Now, it has been lifted there too, replaced with a models eye view rule of shooting, meaning there is few places where you can hide, but the cover saves have gone up in accordance.
Warhammer is still more abstract. And that is bloody good. Accept that. You CANT see what is beyond the front units clearly. Dust, spearpoints, tunnelvision etc works against that. You must either be on a hill OR the units behind better be a big ugly dragon or similar that you simply cannot avoid to see.
And who knows, those orcsies my be hunkering down abit, using the gobbos as a way of getting at your cowardly warmachines. And gobbos are meant to be used like that.