Why do you advocate against new (hero) class? Don't you like the adventorous feeling you get when you first enter Azeroth with a new (hero) class and relearn everything compared to the other classes where you know everything about them with your eyes closed? Greatest thing that ever happened to this game is the implementation of DK's, and I played since vanilla. This game will never be balanced so no excuses about pvp being ruined, and like it isn't already at this state? I don't care for elaboration waste of time, and everyone with a IQ higher then a seagull will understand what I mean.
So lets get to it. First step to solve a problem is to admit you have a problem. Here is my one step programme let the joy in.
Possible Hero classes for expac 5
Dark Ranger (Best possible choice for all the right reasons for any expansion you know why)
Demon Hunter (I know I know but its possible, warglaives)
Tinker (Look above in the brackets, Tinkerer and Alchemist are unused in the WC3 universe and if you say collides with engineering seriously how many have maxed engineering, or a high enough lvl to see its gadgets as well as the recipes to get those gadgets.)
Blademaster (Windwalker spell all I can think off that isn't implemented already in arms warr, but one spell can make all the difference righ?)
Necromancer (Same thing applies here for the demon hunter and tinkerer could easily be introduced with a expansion refocusing on Bolvar)
Runemaster (Don't really like this idea but if Blizz can pull it off in a sophisticated manner why not)
Spellbreaker?
Timewalker (If you think tinkerer is bad you should see this one)
Blood mage (IF 4th specs are introduced)
Warden (I'm afraid this is even worse and harder to implement then demon hunter or necromancer both of them combined)
Shadow Hunter (This a favorite now that Vol'jin is warchief its a golden time to pass it around the ancient teachings of the lua that is. Could be ranged as well)
Witch Doctor (Probably overlaps with shamaN)
Simple Arithmetics 101
new race(s) + expansion = pocket of money
new class(s) + expansion = hammock of money
new hero class(s) + expansion = the titanic aint got shit on this of money
thus new hero class>class>new race