I use quite a few, but there are good ways to cut down on the number you use. First of all, I use JNGP and it allows me to make certain tiles unwalkable. I can, for instance, use a rocky tile for cliffs and make them unwalkable that way. You can also make custom sized pathing blockers. I use ones that are 2x8, 4x8, 8x8, 12x4, etc. This really helps you use fewer. I have also heard that making doodads into pathing blockers instead of destructibles is better. Especially if you don't ever want to remove them.