Warrior: Stitches or Muradin

Stitches is just so incredibly strong. His hook is just plain nasty, he can wipe entire waves with slam and talent it into a massive aoe stun, and his e gives him sustain for days. Gorge turns a 5v5 into a 5v4 super quick. Muradin because he can just lock people down with his stuns. Dwarf Toss is an amazing gap closer and Avatar makes him feel nigh unkillable.

Assassin: Valla (Ranged) / Illidan/Zeratul (Melee)

Valla has insane damage and with her movement speed buff and vault to get away can stay alive for seemingly ever. Illidan and Zeratul however FEEL like assassins. Illidan is just bouncing all over and murdering the enemy team willy-nilly and Zeratul is the opposite, lying in wait for the perfect moment and then BOOM you are waiting to res.

Specialist: Zagarra or Nazeebo // Honorable mention: Gazlowe

Zagarra and Nazeebo are probably my absolute two favorite heros to play. Their kits are just FUN. If I'm not trying to fulfill a daily and just playing a game for fun, I'm going to pick one of these two almost every time. Gazlowe is also a lot of fun but very niche. I love playing the Robo-Goblin Merc Killer build where you just roam and take every camp. It's very much a one trick pony and once the enemy team knows whats up, they will know where you're going to be most of the time. It's fun to solo a boss though.

Support: LiLi or Uther // Honorable mention: Tassadar

Support is probably my least favorite role but you really feel like a champ with Lili when you have dropped a healing totem and use Jug of 1000 cups. Your team is nearly unkillable in a small area. Uther has a more well rounded kit however. Put in a lane with an assassin and his stun sets up a kill while he's topping off their health. Tassadar gets an honorable mention because he's not really a support. If he was properly classified as an assassin, he would be my favorite one. He does insane damage. Insane.