I tried balance accuracy, neatness and usefulness when deciding on hero placement.
Categories should be fairly clear but a complete list is at the bottom. The layout is basically divided by attribute and role such as carry, support, ganker and those that fall in between.
Each category is also organized by the strength of the heroes disables, those with the most hard stuns are closer to the top left, heroes with slows, silences and other disables also ranking before those with no disables.
For example in the intelligence nuker category lion is top left with one stun and one hex, next is lina with a single stun, although skywrath posseses both a slow and a silence zeus comes before him as he posses a ministun.
Earth spirit should be to the right of timbersaw and ember spirit to the right of juggernaught for now.
list of categories from top left to bottom right:
int mid - str mid - agi mid - rng agi car - str gnk - big ult - nuker - support - misc - str misc - str car - mel agi car - agi gnk - str sup - int misc - sup jungle