Just wondering if a complete list of all playable characters is available somewhere. A forum search revealed nothing... thanks! 

In fact, there's none here.

Here are the 56 official Heroes, presented in alphabetical order and divided between Runebound products in chronological order. Please don't ask me to list down also abilities & stats of each. I think I'll die in the middle of my effort.

Base Game (12):

Battlemage Jaes

Bogran the Shadow

Mad Carthos

Mordrog

One Fist

Red Scorpion

Ronan of the Wild

Runewitch Astarra

Silhouette

Sir Valadir

Spiritspeaker Mok

Varikas the Dead

Isle of Dread (8):

Andira Runehand

Grey Ker

Ispher

Landrec the Wise

Lyssa of the East (typo on card: Rune Enchantress)

Steelhorns

Trenloe the Strong

Vyrah the Falconer

Midnight (8, out of print and not Terrinoth-based):

Ciridin

Elaria

Gyruk Kinslayer

Harthan Axecaster

Jaena of Sharuun

Kael, Son of Gurin

Mirala Goodtide

Telvan and Orcbane

Sands of Al-Kalim (6):

Aurim the Sorcerer

Corbin the Axebearer

Eliam the Dervish

Kirga the Tracker

Sahla the Shaman

Tahlia the Thief

Frozen Wastes (6):

Arvel Worldwalker

Laughin Buldar

Karnon

Okaluk and Rakash

Shiver

Zyla

Mists of Zanaga (6):

Annen the Trailblazer

Kala the Hunter

Maliki the Claw

Runemaker Tara

Saka and Kuto

Spiritspeaker Elga

Bonus Heroes (4, released in limited number by FFG in 2010):

Jonas the Kind

Nara the Fang (also available in 1st print of Descent:Sea of Blood)

Tobin Farslayer

Truthseer Kel

Dungeonquest Heroes (6, in FFG Dungeonquest game you will find also the Hero cards for Descent, Runebound and Runewars):

Brother Gherinn

Challara and Brightblaze

Hugo the Glorious

Lindel

Krutzbeck

Tatianna

 Cool thank you sir... looks like I'll be adding DungeonQuest to my list as well then!