TL;DR It's really mission related.
1) not the same role
2) Cargo compartment is important (see below)
3) Soviet doctrine had helicopters fighting with troops so I'm guessing a soldier on the ground is more worried about the dude with the AK-47 and bayonet charging them so they don't have time to take pot shots at choppers
4) Mast mounted radar came later. The original Apache didn't have it and even the new Super Cobra doesn't have it
I'll expand on my comment about the Mi-28 Havoc below but to stab at the Mi-35 you have to look at the Soviet air doctrine when these aircraft were designed.
This student research paper aptly named The Soviet Attack Helicopter describes the role helicopters were seen taking in the Soviet Union
In April of 1976, Belov reflected an evolutionary change in Soviet attitude toward attack helicopters stating that fire-support helicopters may be regarded as a highly effective weapon for land forces. He felt that these helicopters could be used not only to support subunits on the battlefield but also to destroy various targets independently, to accompany airmobile troops and landing forces both inflight and after landing, to fight tanks and other armored targets and also to destroy enemy aircraft and air-mobile troops both in the air and on the ground.
Contrast this to US forces where there are very defined roles for helicopters. Attack helicopters at the time (Apaches and Cobras) and transport units (Huey and Chinook) had very defined roles. Transport choppers provided some cover fire and limited rocket capability. Attack helicopters provided close air support and sneak attacks on various mechanized and fixed targets.
the soviets though saw helicopters as one in the same. As one author put it in the soviet tactical air doctrine paper from 1976
The one constant in all Soviet use of tactical air power is that air power is only one component that must be used in concert with other military forces in order to be effective.
So their helicopters were not tools that happen to occasionally transport or support ground troops they saw them as integral components in a land/air strategy.
this brings me to the Mi-28 Havoc. Note that on the wikipedia page it looks similar to an Apache. Swiveling gun turret, guided/unguided rockets, etc... But also note it has a small compartment that can fit 3 people.
Imagine an aircraft goes down: pilot, co-pilot, navigator (or some combo like that). In the US an attack helicopter would provide cover fire if needed. a transport helicopter would come in to retrieve the crewman.
BUT in the Soviet strategy even the smaller Havoc could land quickly and evacuate the wounded! It's a stark contrast in CONOPS.
The Mi-35 is really a big version of this strategy. Bring in lots of troops and stick around with rockets and guns to provide heavy gun fire. Unlike the precise shots that the Apache/Havoc can take; the Mi-35 and even the armed versions of Huey's/Black Hawks provide a 'pray and spray' mentality. A lot of fire on a lot of entrenched troops/light armor in a treeline or foxholes.