If you really think this is the way to use attack choppers against terrorists which has doçka and manpads
Then you are really stupid, and there is nothing to talk about
In both the war in Iraq and the war in Afghanistan, coalition helicopters in combat operations used tactics which were a far cry from traditional Cold war doctrine.
In the days of the Cold war, attack helicopters were expected to operate in, engage with and survive in, a SAM and AAA rich environment. For this reason Western helicopters had first rate optics and sensors, and their crews were trained to fly low and fast, carefully using the terrain to negate radar operated anti-air weaponry. In this, a helicopter has an inherent advantage over fixed wing aircraft- they can hover, or fly very slowly, in and amongst trees and the terrain, whereas aircraft like the A-10 and Harrier would be at risk of simply crashing if they attempted to do this.
In both Iraq and Afghanistan, the AAA and SAM threat virtually disappeared. Now the main threat was heavier automatic machine guns like the DShK, largely aimed with the old fashioned mk1 eyeball with consequent penalties in range and effectiveness. Instead of highly sophisticated SAM systems, you now had totally unguided RPG type weapons, but primed to explode at a particular range.
As a result of this, it was now safer for Apache aircrew to fly higher, beyond the range of most small arms, and engage at distances which minimised the risk from RPGs. They were able to do this because even the 30mm cannon on the Apache had an effective range of 1500m and beyond, whereas hellfire and 2.75 inch rockets had ranges in excess of 5km- neatly beyond the threat posed by most of the typical weaponry insurgents were likely to obtain. It was also helpful that most recent Western aircraft have received substantial avionics and cockpit upgrades in the last few decades. Apache was of course high up on the list in this regard, a it's sensors, radar, threat receivers and optics are probably all nearly as good as money can buy- compare the Gulf War 1 gun camera footage to that shown by American forces in more recent times. Now even single enemy combatants can be spotted easily in all weathers and at night, at ranges that put the attacking helicopter out of direct earshot of the persons being targeted.
But this is all somewhat besides the point. The question asked was about the tactics adopted by Russian forces in Syria. I believe the reason is basically related to the same reasons NATO forces trained as they did 30 or 40 years ago- the Russians are flying low and very fast in an attempt to make SAM and AAA weaponry less effective. A lot of documented footage has shown rebels using various kinds of MANPADs to down hostile aircraft, both rotary and fixed wing. Clearly, the Russians believe that the insurgents still have access to these weapons and so are using tactics one might use to combat the threat they do. You will see that most of their attacks are carried out by more than one aircraft at a time- so any SAMs launched can be spotted quickly and attacked without delay, and so even a downed aircrew can be aided by their wingman.
I also surmise (but have no evidence) that the quality of the sensors and optics on a typical Russian Mi-24 are not as high quality as those on the Apache or similar in the West and so mean shorter ranges or salvos of unguided weapons are used instead.
https://www.quora.com/Why-do-Russian-helicopters-in-Syria-fly-so-low
Read this bro.