@timmymagic - I will agree with you that all platforms eventually become obsolete, I will have to disagree that the AH is at that point.
You said - "If an AH has to fire from such a long range (and low altitude)…what is the point of the extra expense of a helicopter....you may as well use a drone or fixed wing..." The reason they operate at low altitude in a high threat environment is that they are staying underneath the radar horizon of those ADA that are looking for them, as well as the UAV and the fighters. While drones have a function the mortality rate on them in a high threat environment is
very high. I have heard that the expected life is something like three hours. Why are there pleas to have more UAV sent, Where are the UAV that were until recently masters of reconnaissance? As well as their lack of survivability they don't work as well in sub-optimal weather. In fairness nothing does, but a 16,000 lbs. platform is not as susceptible to weather conditions as a 1600 lbs., let alone 16 lbs. platform.
You said - "If you can't get eyes on a target or operate within your sensor range (like the US plans to do with AH-64 with Spike...) then what benefit does a very expensive AH bring?" By this logic we ought never have had the expense of any fighters past F-8 Crusader and other late 50's fighters. Nor should we invest in these sort of platforms or missiles any more to fight the BVR fight. Anti-radiation missiles are fired at very long ranges to minimize the time the shooter is in the engagement basket of the air defenses they are trying to defeat. Why are so many missiles types being made to shoot well beyond the range of their targets. "Defeating your enemy without being engaged is the epitome of warfare," to paraphrase one of the Masters of Military Strategy.
You said - "What benefit does an AH have firing Spike just over the horizon, using target acquisition from 'other platforms' have over a ground unit firing a Land Precision Strike missile at far, far lower cost....with greater range and effect on target?" Most countries that have bought Spike have them ground mounted and use them on high pay-off targets non-line of sight sniping). The Spike on the US Apaches are not replacing the AGM-114 and JAGM muntions. They will carry just a few in order to snipe threat ADA that keep them from shooting ATGM at the targets the ground commander wants prosecuted. Until ground vehicles can drive over mountains, rivers, swamps. plowed field, etc., at 150 miles per hour/200+kph having a platform that can maneuver to do that while staying masked from the threat seems a good idea.
Someday the AH will outlive its usefulness. I do not believe that day is today.