wouldn't need to fly at treetop level or hide behind buildings
I dunno about that - a helo (even a specially armoured/equipped) gunship like Apache/Ka-50 is far more vunerable than an A-10/Su-25. Rotors/tail rotors are big target. Check out the Apache deep raid that happened in Iraq in 2003 - Apaches were ambushed, 1 shot down and I seem to recall all came back with significant damage.
In a high threat WarPact vs NATO punch up you'll have SAMs locking up anything that flies above Nap of the Earth, plus you will want to avoid fast movers out for a kill by staying as low as possible to keep in the ground clutter and so the Mark1 eyeball wouldn't see you.
I think the Ka-50 and its counter-insurgency role was not something it was speficially designed for but perhaps something it fell into when the Russian AF realised that the one-pilot combat helo concept only will work in permissive environment.
Don't get me wrong I think its a seriously cool chopper and a great bit of kit - but there were two designs Ka-50 Havoc & Mi-28 Hokum in the running to be the successor to the Mi-24 - and the Russians chose the Mi-28. (despite the Ka-50s having been tested in combat).
In light of Ed's remarks my reading of this was that the workload of the Ka-50 was too heavy for the average squadron pilot and in a full-on conventional war two crew was the way to go.
However for special forces support and anti-guerilla stuff - where you are worrying mosting about AAA and the odd MANPAD its fine - rather than keeping low to avoid an F-15 Eagle spotting you...
Just my two-penneth anyhow...