level design is a field on life support having been stomped on by expensive AAA workflows which have been artificially forced as standard and has fallen into a hellhole where people confuse it with other skills more often than they don't
theory: widespread adoption of modular mesh based workflows and dropping level design tools came out of epic doing it successfully but that only worked because of them
-being super rich
-making games at the time that didn't particularly need strong iterative level design (gears)
-being super rich
-making games at the time that didn't particularly need strong iterative level design (gears)
epic own unreal engine so them doing something means AAA generally does the thing which means indie has to follow unless it really wants to put its back out, which is a problem when they do what every AAA does, which is extremely not-generally-applicable solutions
brb reading The Babysitter's Club 
Here is an interesting, and fucking grim, look into how LD can work in AAA (here Epic). For this dude, "flow" is unattainable and improving LD tools is undesirable because you'll get taken off your level when it starts to look okay. Stockholm syndrome
The best editor out there right now is Hammer 2. The best methodology is what it's always been: whatever gives the designer maximum control, speed, flow, ability to iterate. Keep them in the loop. See:
