I'm now in WoR Maranda to recruit Cyan, so I want to talk about my experience with Mog in WoB, to be more specific, in Floating Continent
I used a 5 Maduin / 5 Shoat Build with Element rods / Gold Shield / Magus Hat / Gold Armor and Stat Stick/Amulet as accesories, and it made a great work there. During the approaching to Floating Continent Mog made a good work dealing with random encounters using Water Rondo. Against Ultros it sticked with Thunder Rod procs dealing a good amount of damage. Against IAF I returned again to use Water Rondo, dealing a great amount of damage to this boss. The Floating Continent was a bit hard but Mog helped against enemies not called Gargoyle (too much magic bulk to be useful) and Behemoth (water resist) with Water Rondo, otherwise, I used Wind Song when I really needed healing.
Against Atma is where Mog shined the most. Black Belt / Amulet protected me against the most dangerous things Atma offered, and Ice 2 procs made around 3700-4000 of damage, sometimes even being able to deal twice more damage due to Black Belt counters. It was surprinsingly consistent despite the randomness Ice 2 procs give.
In previous version I tried X-Magic Mog against Magimaster and heck, it was really useful, making around 16000-20000 of damage when it was weak to Earth, Poison and Wind. I'll try it again in this version to see the results (This is why I like Esper resetting so much)
Mog can be a bit random, but it is certainly useful