Post-healing magic skill update:
See the following item sets for comparison (VIT+ is the same for both sets):
Item set # 255028 - Staff
Total bonuses: +50% Potency, +88~91 Healing Magic Skill, +30 MND
Item set # 256460 - Tefnut / Shield
Total bonuses: 50% potency, +83 skill, +43 MND
The staff build DOES have more skill, but considering 1 skill ~ 2 MND, the +13 MND on the Tefnut set accounts to an extra ~6.5 skill roughly so it would be SLIGHTLY better (+1.5~ skill advantage worth of potency) outside of Lightsday where the Staff build will win regardless.
Suppose it boils down to preference nowadays. Get lucky on Genbu's augments? Use Tefnut. Don't like club/shield? Use staff. There's situations one is better than the other, at least until more gear comes out. There isn't a given "X is always better than Y" here.