The heroes have been picked as the best performing ones from the Divine and Immortal brackets.
The choice of heroes has been made from a combination of high pick rate and high win rate heroes.
Definitely more than two years.
Poison Touch is a 2 seconds AoE disable with a 15 second cooldown, which is absolutely insane!
In comparison, Tidehunters Ravage is a 2.8 second stun with a 140 second cooldown.
In an aggressive lane, Poison Touch can be maxed out to put pressure on the enemy.
This also gives him the ability to play as a position 4 or a position 5 support.
Chen might not have the highest pick rate, but he has the highest win rate amongst supports.
Honorable Mentions
The honorable mentions have two heroes with very high pick rates.
However, Pudge and Dawnbreaker are hardly played only as supports in pubs.
Both heroes are often used in multiple positions, so its hard to decipher what their best position is.
However, both of them are played as supports this meta, and seem to be doing well.