Frontlines FAQs Guide.

[SeraviEdalborez]

I can actually confirm that Protect does in fact boost your Defense in Frontlines. After a WHM kept telling me it does not, I removed his Protect buff and my Defense went from 338 down to 294. I was on BLM and no other buff/food/icons were removed when I canceled my Protect. The icon even states "Defense is enhanced" which leads me to believe that your physical defense is, but not your magical? (it actually might have been the Scholar Protect now that I think of it)

Protect boosts your defense but defense doesn't DO ANYTHING in FL. Or any PvP match type.