From Diablo Wiki
Jeff Strain worked at Blizzard from in the late 1990s and contributed to Diablo I, Diablo 2, StarCraft and World of WarCraft. He left Blizzard in 2000, along with other long time employees Mike O'Brien and Patrick Wyatt, in order to form Arena.net, creators of Guild Wars. After nearly a decade there, Jeff joined NCsoft, and then moved on in late 2009 to found UndeadLabs, where his team is creating a zombie-themed MMORPG.
Comments on Diablo 1
PCGames.de:When you hear the word "Diablo" today you immediately have to think of ... ?
Jeff Strain: Nothing less than the rebirth of the PC RPG. Everyone thought we were crazy at the time, because the RPG genre was presumed dead. It would be tantamount to betting your company on a traditional adventure game today. When I hear "Diablo" I feel proud that I was part of the team that rescued my favorite genre.
PCGames.de:According to Moby Games you were a programmer on the first Diablo. When you were working on that game, could you already anticipate how important it would become, what impact it would have?
Jeff Strain: I had no idea that it would succeed as well as it did. All I knew is that I was excited to play it personally, and I hoped the gamers of the world would love it as much as I did; and of course they did. The best games always come from passionate teams, and I think my personal enthusiasm for what we were making was a pretty good reflection of the rest of the team.
PCGames.de:What "lesson" did we - you as developers and we as gamers - learn from the Diablo games?Jeff Strain: Sometimes you have to plug your ears and go your own way. Diablo would never have happened if we had designed for a focus-test group. Everyone thought we were crazy -- the press, publishers, even a good chunk of vocal gamers who couldn't understand why we weren't cranking out another RTS -- but we could see what it could be and we just barreled on. It's always important to listen to your fans, but you also can't be a feather being blown on the wind. It gets harder for companies to continue to innovate when they grow very large, but I still believe that true excellence requires that we push boundaries and challenge assumptions.
A quick summary from Jeff's page on LinkedIn. 
- Senior Programmer, Blizzard Entertainment, January 1996 - March 2000
- Founder and President, ArenaNet, April 2000 — July 2008
- President, Product Development, NCsoft, July 2008 — August 2009
- Founder, Undead Labs, October 2009 - Present.
Game Design Credits
Jeff Strain has worked on numerous AAA titles during his career in the gaming industry. A few highlights from his online bio. 
- Diablo I -- Installer Programming
- StarCraft -- Campaign Editor
- GuildWars & Expansions -- Executive Producer
- Aion -- Executive Producer
|Blizzard Entertainment & other Game-related Topics  Blizz Games Other Games Terms Devs Blizz ppl D3 D2 D1 Other ppl Events Merchandise Related|
Blizzard All cont.
|Diablo III Team|
|Diablo II Team|