I've had nothing but good experiences as a fresh pld which was my first class. My biggest pieces of advice for you would be this.
1. As a tank I don't go into a new place without at least watching a video on it or reading a guide. The one exception being if I'm with a majority FC run and someone is explaining as we go.
2. Let the group know you are new if it's a 8 or 24 man and you would prefer to OT. They will likely already have figured it out, but it can't hurt to give them a heads up if there is more than one new person or someone just didn't see the notification.