What level are you, and what is your current skill level? And would you be using it to skill up in experience points parties, or in a dedicated skill-up session?
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Avoda (Siren Server) Hume Male NIN90/PLD76/RDM44/WHM63/BLM40/THF40/WAR50 San d'Oria - Rank 10, Bastok - Rank 6 Member of BeastShell
i would say master depending on your skill and what youre trying to skillup on. this is unrelated in a skillup sense but still relevant. i tried using master shield in campaign soloing figuring that more blocks = less damage + more tp. but i found that i had a much easier time surviving with my koenig (~220 skill)
so i think masters is better until you get to a point where the things you have to fight can actually kill you, then use a rank 3
I had the same problem as you. I just Level Synced in the Mire until my shield was at a respectable level. Got PLD to 75. Tried to solo for skill but got fed up of it, so I just went to Dynamis, popped Reprisal, fought Monk mobs and poped sentinel when they use 100fists. Works wonderfully.