From wiki:
http://wiki.ffxiclopedia.org/wiki/Protect_V
Protect V "Enhances target player's defense by 60 points as of June 21st 2010 update. Grants defense bonus equal to that of WHM Protectra V base level spell with one merit." So Tero is correct, for the same 84 MP, WHM Protectra V with 2+ merits will increase DEF more than single-target Protect V.
Based in increments of protect spells 1 starts at 10def and each one there after is +15, But this new spell protect V is only +5 def increase from protect 4. This Spell completely fails to follow logic of progression to what a player actually needs to have for a Protect spell at the protect V's casting level.