I have been trying to find out what these characters actually do for some time now and can't find a single image of their Runewars cards. Is there a reason there are scans or pictures of their Runebound and Descent versions and not their Runewars version? Has FFG said not to release that information? Could someone provide their stats and specials if FFG hasn't said otherwise?

What "Realms of Terrinoth heroes" are we talking about here? The four promo figs? I certainly didn't hear about any new heroes being at the Realms event. If the promo heroes are the ones you mean (Jonas the Kind, Truthseer Kel, Nara the Fang and Tobin Farslayer) then their Runewars hero cards are up on BGG, here:

boardgamegeek.com/images/thing/59294/runewars/page/5

What Steve said. I wasn't at the event, but I was able to buy one of the Realms of Terrinoth gift bags that FFG was selling, and those four heroes were indeed the four that were included.