Humm... the words untouchable, hc and hell don't fit very well together. Monster-flee in hell is also somewhat of a bad idea you see, because yes, while it does work to some degree, in hell mode, the monsters run much faster than usual, and when they are hit with the monster-flee stat, they run extremely fast in the opposite direction for 1-2 seconds, until they reach the destination set in the parameter, then run towards you again. It's almost better not to use it, because while it can help to keep monsters away from you, what it also can do is to push them away, then you run ahead, and then trigger more monster packs, which then can overwhelm you. It simply delays the problem, so to speak.
As far as bow ama goes .. i've played many hc seasons bowa. It is not untouchable by any means, even with very good gear. You will have to play at least halfway defensively if you want to survive. But if you know what you're doing, you can survive well and have fun with it too.
Actually, if you want to play a safe ama build, i recommend frostmaiden. Though it is quite expensive and needs a bit of practice to play right, it is very fun and also actually quite safe, since you freeze everything to a halt, also shattering most if not all corpses.
D2:R