Of PvP & Protect Spell

[Umo]

Last night I joined a Frontline campaign in progress. I ran to the Heliodrome in order to join my party and defeat as many drones as possible. Once done, I went back to our outpost and came by a fellow white mage, so I asked him/her to use Protect on me since I didn't join the match from the start.
S/he was not afk, but Protect was not being casted, so I asked again since I had to run to help another alliance. S/he then said "sure, but Protect is useless anyways".
I was a bit shocked, but there were more important matters at hand, so I /bow and left.

Later on, our outpost was being attacked. I ran to the flag and had to fight as BRD against a DRG and a WAR. Protect was still on (19 mins. remaining), so I managed myself to survive for a decent amount of time. I was about to die when this WHM came by and saved me by a whisker. Then, once the outpost was safe again, we hold this short conversation:


Today I have not yet found those guides. Despite of this, I feel Protect works just fine on PvP, but I might be wrong, so could you please enlighten me about this matter?
Note I'm not saying Protect is a life-saver, but it's useful, isn't it?