wie hast Du die Pakete abgefragt, also so das man weiss die gehören zu gnome?
Ich installiere Arch mit Scripten, da habe ich es gerade rauskopiert. 
So siehts im Original aus.
Bash
#!/bin/bash
## Gnome-Desktop
arch-chroot /mnt pacman -S --noconfirm --needed gnome-shell
arch-chroot /mnt pacman -S --noconfirm --needed gnome-control-center
arch-chroot /mnt pacman -S --noconfirm --needed gnome-terminal
arch-chroot /mnt pacman -S --noconfirm --needed gnome-system-monitor
arch-chroot /mnt pacman -S --noconfirm --needed nautilus
arch-chroot /mnt pacman -S --noconfirm --needed sushi
arch-chroot /mnt pacman -S --noconfirm --needed gnome-keyring
arch-chroot /mnt pacman -S --noconfirm --needed gnome-calendar
arch-chroot /mnt pacman -S --noconfirm --needed gnome-calculator
arch-chroot /mnt pacman -S --noconfirm --needed gnome-backgrounds
arch-chroot /mnt pacman -S --noconfirm --needed evince
arch-chroot /mnt pacman -S --noconfirm --needed file-roller
arch-chroot /mnt pacman -S --noconfirm --needed loupe
arch-chroot /mnt pacman -S --noconfirm --needed shotwell
arch-chroot /mnt pacman -S --noconfirm --needed gnome-podcasts
arch-chroot /mnt pacman -S --noconfirm --needed gnome-software
arch-chroot /mnt pacman -S --noconfirm --needed totem
arch-chroot /mnt pacman -S --noconfirm --needed gnome-maps
arch-chroot /mnt pacman -S --noconfirm --needed gnome-text-editor
arch-chroot /mnt pacman -S --noconfirm --needed dconf-editor
arch-chroot /mnt pacman -S --noconfirm --needed gnome-tweaks
arch-chroot /mnt pacman -S --noconfirm --needed gnome-themes-extra
arch-chroot /mnt pacman -S --noconfirm --needed seahorse
arch-chroot /mnt pacman -S --noconfirm --needed power-profiles-daemon
arch-chroot /mnt pacman -S --noconfirm --needed nautilus-image-converter
arch-chroot /mnt pacman -S --noconfirm --needed gvfs-mtp
arch-chroot /mnt pacman -S --noconfirm --needed gvfs-nfs
arch-chroot /mnt pacman -S --noconfirm --needed gvfs-smb
## Login-Manager
arch-chroot /mnt pacman -S --noconfirm --needed gdm
arch-chroot /mnt systemctl enable gdm.service