Many- perhaps most here- find good smoking all the way through a bowl.
I may find good smoking all the way down or half way down. If it goes bad part way down, often if I break it away from the side wall a bit or let it rest a little, then light it again, it improves greatly and smokes further.
Virginias seem to stove as I smoke them. They get softer and smoother and sweeter.
This goes in hand with what I was going to say on another thread about lighting. Some people don't think it necessary to go through a singe and a sear light (giving it a several minute rest afterwards), but I read something once about it setting up the sugars, allows starches to convert to sugars, maybe through a process called decarboxilization (something I need to read up further on), and there seems to be something to it. Whether by heat or drying or both, this seems to set the tobacco up for better flavor and better burning. Seems to work for me since I began doing it.
As to pipe rocks, I wonder if this at all works like one pipe I have made by Combusto, which has a thread in metal plug at the bottom?
As to the bottom of the bowl, I agree, the very bottom is never great, how close you get to it before things go south depends on many things from the tobacco, the pack, the pipe, to how you smoke it. But I try to get at least 3/4ths of the bowl smoked and leave a little at the bottom to have soaked up as much tar as possible.