Had mobs climb up stuff after me previously, but yeah no longer seen it now.
Guess vines do ok then, but the circular wood staircase isn't a problem either.
Seriously, don't do a staircase. Mobs can climb circular staircases now. I was on Trifax's server the other day in Ike's basement. It was a bedroom, and there was a spiral staircase down into the mines next to the be. Suddenly, a zombie pops out. It climbed up the staircase like it was nothing. We closed that off with a door after that, and more came up later on. Luckily the door stopped them. Use vines - as Anybody said, since mobs no longer walk into walls like morons, they don't climb.
Also, they can find entrances now. I made a small room in a hill next to the house, and zombies started coming up behind me while I was doing stuff. Had to put a door there, too.