You need to have x11-drivers/xf86-video-intel installed too. It used to be a dependency of the full x11/xorg installation but that's not the case any more (look at x11-drivers/xorg-drivers). No need to recompile x11/xorg-drivers from ports, just install x11-drivers/xf86-video-intel.
That was it, thank you. Working flawlessly now.