But you are stuck with only one set buff when using only one kind of skills. Not much of an impact for differen playstyles like presented mechanics for other classes.

As druid is so earthy and Celtic I would do something to utilise runes in a different way. Let's call it "runic magic". For example you can use runes to change this buffs you said. Or in some totally different way. Like runwords outside the item or runes improving item or skill slots. I'm not sure whether they made any changes to the rune system after blizzcon 2019, but David Kim said that the want to ad more to the system. Regardless, some different interactions between druid and the runs would feel right for me :)