Ion's been with Blizzard since 2008, prior to which he worked in law as an associate in a Washington, DC-based firm. Since joining Blizzard he's worked not only on raid boss and encounter design, but also on class design and balance, the achievement system, and more. If you want to see more information on what Ion's been up to lately, and in the past, you can rifle through all WoW Insider's articles relating to his famously wordy forum posts! In the meantime, head over and follow him on Twitter.
You can also check out Zarhym's official list of Blizzard employees, fansites and other useful resources on Twitter and other social media.