Should they have a small shield covering them so they won't be totally exposed? In real life when someone brings a mounted turret, it is fearsome. Or does the car and turret provide enough shield already?
yes or no?

In the far far future, weapon engineers didn't realise they could take advantage of a mobile weapon platform with a built in near infinite power source, so they stuck the weakest weapons they could find on them.

The also designed said vehicles, built for warfare, without any protection for the driver and crew. No even a windshield.

True. As opposed to modern LAVs, the ones in Dust514 seem more like a throwback to WWII style LAVs

Personally ... I don't have a problem with that, since a LAV seems more positioned as a light, fast, transport, with the gun as an after-thought, as opposed to a HAV where the gun is primary and the transport part is secondary.

When we get MAVs, I'd expect them to include at least 1 enclosed small turret, then again, maybe not. You risk sticking your head out to shoot from a non-moving vehicle, expect you might get hit.

I think it is funny when they stop to swap to the turret and then DIAF as I either insert scrambler rounds into their dropsuit or chuck an AV nade or 3 at them.

Stopping and becoming stationary to switch to the turret should be a very risky tactic, no mechanic should be added to change that.

I do find it appropriate, however, that I can snipe the head of the driver if he sits still just long enough in the right spot. That was an awesome, very rare, shot that should never be nerfed :)