If by "includes TWO staff members who used to work at Black Isle" means Obsidian is Black Isle, then yes. A company, in my view, is the development staff - not the name. And Obsidian is down to two members of Black Isle at this point. Regardless of their legacy, they no longer qualify as Black Isle in my eyes.
Don't get me wrong, I love Obsidian. Alpha Protocol is actually one of my favorite games.
Obsidian's humor is different from Bethesda's humor. As someone else said, Obsidian likes to make pop-culture references. Bethesda likes to make tongue-in-cheek jokes. I think Bethesda's humor has a bit more legs to it.
Some of Black Isle's pop culture references feel incredibly dated now when playing through Fallout 2. I think teddy bears screwing and shooting up drugs is more timeless. I mean, it's not running into the crew of the Next Generation, but still.....