I've had three extremely successful ranged carry games with all passives in Ability Draft mode.
First was Razor, with Moment of Courage (Legionaire's passive lifesteal on hit proc), Time Lock (Faceless Void's stun proc), Essence Shift (Slark's "steal 1 of each stat and get 3 agility for 2 minutes on hit"), and Stampede (Centaur's ultimate, speed boost) as a throwaway.
Second was Drow, with Time Lock, Berserker's Blood (Huskar's passive that gives attack speed/magic armor as you get lower on life), Juxtapose (Phantom Lancer's image spawning proc) and Chemical Rage (Alchemist's overpowered ult). Probably my overall best game.
Third was Sniper with Moment of Courage, Fury Swipes (Ursa's stacking damage on each consecutive hit), Take Aim (Sniper's range increaser passive), and Venomous Gale as a throwaway ultimate. Ranged characters should NEVER be able to get Fury Swipes. Early lane harassment is a joke compared to someone with 1k range poking you for more damage each hit.
Any agility carry with Chemical Rage is a bit overpowered, considering they don't suffer from the lack of agility growth that Alchemist does, and benefit more from the decreased base attack timer, but a Drow with a Bash and more attack speed the closer to death she gets, all whilst spawning up to 7 clones? That's the definition of broken, even though Juxtapose was my throwaway pick. Moment of Courage is a welcome addition to any carry's survivability, since the extra hit can also proc orb effects, such as Fury Swipes, Bash, etc.
I suppose part of the fun is getting a character whose base stats, movespeed and growth fit the kit you are trying to build. I had a bit of fun with a Witch Doctor who had Spiritbreaker's Charge and Nether Strike, Dragon Knight's Dragon Tail stun, and his own Maledict. Charge in, stunning them for 2.4 seconds, Maledict, stun again for 3.25 seconds, and Dagon or ult them. Rinse repeat every 30 seconds.
But for every good build there are the terrible ones, as some don't know the game well enough to know what certain characters are capable of, or what they should be doing for certain roles. It certainly makes the game more interesting.