Didn't remember that was a thing. Now I'm not sure wether I want the two abilities merged or if it should stay as is...
Just leave as is. Hunter:Wizard is probably one of the better hunters anyway since wizards are a large class its usually worth while running it. Adding shaman to it will make it over the top as it will punish some factions heavily such as KF and FS who both have an abundance of playable runes which belong to these classes.
i think you misunderstand the issue here with your suggestion. and the word abundance. As you said witch is relegated to FW. so it isn't as wide scale in its effect. whereas shaman and wizard are ABUNDANT across the game both in mneta and theme. Cyclops for example in SP contain laregly shamans and wizards as do Voil. Witch as you just stated isn't abundant and therefore isn't game breaking in having that effect alongside wizard. I'm not sure you understand your own suggestion, or your own argument. Therefore would state you have no merit.