No... The boss fight is in a BIG room and you need that, especially with ranged characters, to fight him! So, popping it up randomly on the map would make for some very awkward fights and would probably even make the boss bug if he cannot move around as intended!

It's fine as it is, you just rush too much if you miss having enough mob kills!

it can be a few bigger rooms and he spawns to the closest spot, acutally untained runs are quite ok, but normal ones, too low denisity, and sometimes u need to turn back all the map and go again to boss room