New with bosses need help

hey guys, I stopped playing around 8.6 and came back. I keep reading everyone is doing bosses etc. never done any except the ones on new rook island. I was wondering what would be the best way to try them. is this by doing grizzly Adams tasks? and I am talking low lvls like 50+ . also a lot of people recommend rp or monk. do you guys think after the rebalance patch they will still be best/easiest classes to run bosses solo? thanks!