Cairne's death was stupid. He received no development since the beginning of Classic WoW. At least Baine should now be given story time. Vol'jin died to make room for Sylvanas... incredibly stupid story writing. Could've had story time for both. Rokhan is nowhere to be seen except some occasional appearances. Same with Rexxar. Gallywix should be replaced with Gazlowe and Ji Firepaw should be replaced with Chen. And Thrall must finally come back, as the Thrall from WC3.
2 very important characters were killed without much development - Cairne and Vol'jin.
4 very important characters have been in the shadows - Rexxar, Rokhan, Gazlowe, Nazgrel.
1 very important character is in the wrong place - Chen.
As a Horde fan, this is my problem. Killing characters is a one way ticket. Since you can't bring Cairne and Vol'jin back, give them some story time as spirits (Vol'jin, at least, is getting some in BFA). Develop their replacements - Baine and Rokhan.