There are 2 rune rocks by the lava maze, 2 in hero's guild, 1 in the dungeon under the lava maze, and 1 in the mourner's caves under ardougne. So that's 6 total.
This would be too restricting. I try to keep my total level 14x that of my combat, but I don't see why Jagex has to force us to have a certain skill total.