At the time of my hire Blizzard Entertainment was still utilizing an on-site recruiter. This is no longer the case and they only hire from temp agencies. However, this was the experience previously:
1) Contacted by on-site recruiter who would give preliminary phone screen
2) Phone Screen would include expectations (recruiter was very clear that deep nights and weekends were required)
3) On-site interview scheduled
4) On-site interview consisted of a one-on-one with a "Senior" which is the highest possible Tier of Support you can reach before Team Manager.
On-site interview was very candid - asked about my knowledge of Blizzard products (of which I have extensive knowledge) and general experience as a gamer. Also asked general customer support style questions. Overall, interview was very casual and friendly.