I've always assumed Protect is more important than just 10% more def O.o I remember running around in S. Thanalan while levelling, and those sabotenders with their 100 needles did 100 damage without Protect, 50 damage with Protect (non-boosted). Maybe attacks like that are treated differently?

But yeah, for those first dungeons.... Sure, Protect is always nice and it's like hugging your security blanket tightly But I wouldn't throw a fit right at the start. If it turned out the party had trouble surviving, however, I'd request the healer (or anyone with access to CNJ crossclass skills, really) to shuffle their skills around for a quick boost. And should you happen to have people still in classes instead of jobs, which seems more likely if you have trouble surviving without Protect, it's probably even easier to find someone with access to skill slots for Protect =)