Riding full throttle is not practical all of the time, and neither is blowing controllers
I still recommend running at least 80% throttle or higher as much as possible if you want to use an R/C controller. Sorry if you don't like it.
Torque is derived from RMS power, battery amps do correlate with it directly. Less battery amps do not mean less phase amps unless the load is reduced as well (such as wind resistance) or if the controller is amp based control instead of voltage based (ie 50% throttle means 50% of max motor and battery amps). Flat roads won't kill a setup that is geared properly with a battery amp limited controller, but the hills can
Let us say you have your R/C controller that is 20a battery limited. Start from 0mph on a hill that will eat 20 amps all the way up, and if you are a heavy guy it will take a looooong time to get up to speed. To keep the battery current at 20a the duty cycle will be very low at first. The first .5 seconds may even be under 5% duty- which is 400 amps on the FETs. Since an R/C controller isn't smart enough to watch the motor amps, it will happily chug along at 5% duty cycle since the battery current limiter tells it so. Pow, Pow, Pow, can you hear the FETs crying for that first few half seconds?
IF there were motor amp limiting as well, the controller could have a 60a motor limit set. Now this same situation makes the controller say wow- 400a is way too much! I will throttle back further to decrease the load because of this nasty low duty cycle. In this situation the controller would have to stop all together since the hill is already causing the 20 amp load. In fact, it wouldn't even get started. You would have to hit the hill running 33.3% duty cycle or more to have hope to get up it on electric power only.
I too have great experience with the throttle response of the Castle controllers. They are worlds above any Xie Chang I have used. They certainly have a place and can be used with great success (I beat on an HV160 regularly), but you have to know the limits and ways to use them.