Welcome back! :)
Forums have kinda been the same old same old. You're coming back at a perfect time as far as catch-up mechanics go. You've got Order Halls and their class mounts as well as some cool class fantasy with Artifacts. Story-wise we've made it to the planet Argus (home of the Legion) and we're getting ready to assault the Stronghold of the Legion, Antorus. You'll understand when you play through and watch some cinematics so I'll keep spoilers to a minimum :P
PvP wise have been interesting so far with Brawls, which are a pretty unique spin on battlegrounds that breaks up the usual formula of how we've done them, so I recommend checking that out. The prestige system offers an additional PVP-only talent tree you can use as you level up with Honor that gives you some choice for different setups, comps, arenas, or bgs.
I've mainly been focusing on getting all my alts caught up in the story for World Quests and Emissaries. Once I finish that up I do the usual cherry picking of my characters on who I want to pvp/raid with.