Heroes are already a strong unit which is able to become a game changer, many players dont like and expressed their complains about heroes being so strong, and we are not going to "Buff Heroes more", just to reduce the game length, which will cause bigger snowballs that what already the game has.
Buffing heroes is not the way to go, they actually need a different game mechanic which is something i am already have been thinkink about.
Marine Arena had passed the test having 45 minutes SD during the first years, and this showed to be a very good amount of time, which gives both a chance for a comeback and making the game length shorter.
When 2 teams left indeed there's no other players to feed, but knowing that in 10 minutes SD will occour, the feeded team will just camp with tanks, sentries etc. (thats a very usual think), and they will wait for 10 minutes to pass. Having a 10 min SD if only 2 teams left during 20 minutes of game time, has a big difference compared to 45 min SD, which the other team can use that time and try to turn the game.
If a hero is buffed in a way to turn a 4k bounty difference in just 10 minutes having only 1 enemy team or being able to feed more than what SD gives (100 minerals every 20 seconds), imagine what this hero would be able to do early game when there's 3 enemy teams to get feed from.
Still this is on discussion level, but will move into testing ground and we will see how things are before moving in implementing this to a public level.