It would be the same as `pacman -Ss base` plus `pacman -Ss base-devel`. Note "-Ssq" would probably be much more useful in this context.
If you are worried about download limits, you should install base but not base-devel. Without base, there is a fair chance you will not have a functional system. Base-devel is only needed for using the AUR, but it is quite easy to get a working system without anything from base-devel.
I have no idea how yaourt (fails to) work(s), but FWIW the pacman command you used could be simplified - both the command and the processing needed would be reduced:pacman -Qim | grep -E "Name : xf".+devel