This could spark quite the interesting discussion... First, I've almost never tried to talk to a ground unit via Havequick I/II. Single channel secure or SINGARS is the only thing I've ever used. I have used Havequick to talk interflight, and in our aircraft it's the opposite. Havequick is way easier than SINGARS. Unless there were good SOPs in place, talking SINGARS was painful at best (because our time is constantly downloaded from the GPS), because if the ground unit doesn't use a PLGR enough, we can't talk. As I'm sure you well know, the PRC-119 is notorious for losing time.
Of course, talking to a helo on UHF has its limitations, but it's all a factor of the radio/power. I'm assuming your reference to screwed is using a manpack radio. The PRC-148 is pathetic, not enough power without the amp. The PRC-113 is better (more power), and the PRC-117 is best for a manpack. Still have that pesky line-of-sight issue. Using the MRC-148 is a whole different ball game, I had no issues - could never see the aircraft, and could talk to them sometimes close to 15 miles away. Throw in the fact that I didn't have to walk anywhere, had UHF/VHF/HQ/SINGARS/SATCOM/HF, and an ass ton of power, and I was a happy man...