Theres no 'set' amount of HP needed before the Latent Effect kicks in. But there is a 'set' percentage of HP before it kicks in. And this 'percentage' isnt set for each piece of armor you equip that has the Latent Effect.
Example>>>>
The carapace set @ Lv 61
The Latent Effects dont kick in until your HP is @ 1/5th or less. And you can clearly view this in your Equptment Menu. (total Attack and Defense) Whislt the Lv50 Job specific Rings (Fencers Ring Lv 50RDM for example) will kick in @1/4 percent HP.
Actually since Warlock gear is RDM AF I think it only matters if you have RDM as either main or sub. It would kinda be pointless if it's RDM AF only to have to find out that you'd have to have RDM subbed. Its probably based on hp not job.
My main job is BLM/RDM and my secondary is BRD/RDM. Obviously this is my dream cape. I have attempted the BCNM30 that drops it (Toadal Recall 6-man in Ghelsba Outpost) but it is extremely difficult. All four of the toadstools you fight are TP freaks, and their attacks do about 80 damage per hit even if you're well-equipped.
I assume that this Latent Effect is unlocked by putting RDM as your subjob. Does anyone know if my assumption is correct? It would be a good mantle for a brd/rdm and might make rdm worth subbing for a bard.
A Red Mage gets "Fast Cast" at lvl 15. So the mantle would be useful from lvl 15 on as a RDM or RDM subjob. So yes it would be good for a BRD/RDM if your BRD were lvl 30, which would make your RDM lvl 15...which would make "fast cast" available to you.