Hello Trix, we use discord 50% of the time we're playing together. But voice chatting is entirely voluntary so not everyone will be online at the same time on voice.
But during 24man raids and what not, or hard content such as 4man/6man of the raid version, we will definitely use the said voice call program to communicate.
you can follow our clan discord link once you join, and try it out with us, if you like it you're welcome to stay with us, if not then, you can always leave on a positive note, doesn't hurt right ^^/