Definitely pay some attention to doing quests and experiencing the content. The lore is diverse and interesting and some of the stories told in the game are very fun or captivating.
I like the Battlemage the most. I have a lvl 194 battlemage in renegades, a lvl 166 battlemage in reboot, and a lvl 172 battlmage also in reboot. I like to play it because there is always a lot going on for a relatively simple and satisfying play style. It is also kind of a mix between a mage and a warrior, which are my two favorite classes. It is also a very balanced class, having good offensive, defensive, and plenty of support skills. Also cant forget the 100% knock back resistance. It is also, in my opinion, one of the most unique classes available. Oh and you get an adorable grim reaper follower that turns into a demon that destroys everything occasionally.