So general consensus seems to be that this upcoming event dungeon isn't worth it. Supposedly the 2 battle abilities are fairly meh, and the HP+15% is really hard to get, due to it being tied to a rare encounter with a rare drop chance.
There is a whole lot of kneejerking going on in the Reddit atm over this event. People proclaiming the end of the world, dogs and cats living together, Exdeath, Kuja, and Emperor trysts, and all that nonsense.
In reality, people are pissed off because they believe the event is going to be similar to the demon heart event from last week, which is not that far from the truth. However, in this event (if it follows JP), insane quantities of materials are replaced with rare drop rates and low material requirements.
Just like the gravity rod, all of these rewards are incremental upgrades. Reddit is pissed off because the event is not handing out "I win" buttons to everyone on easy mode. The jewel of the event is the craftable HP +15% ability/materia, which requires farming a boss that is roughly as difficult as Demon Chimera (stats, resists, HP pool, etc). The kicker here is that the boss is only weak against earth and practically immune to everything else. So, the boss can either be burnt through extreme physical DPS (barrage, etc), or you can farm/craft multiple Stonra Blades to give everyone an ability that the boss is weak against (not that Reddit would ever think of that, all they are bitching about is why Stonra Blade is not AoE).
Should be an interesting event, at least for experimentation purposes. I can see myself farming at least 1 HP materia, depending on how rare the drops are. That said, if the drop is a "rare or nothing" drop from the boss, then wouldn't bringing a friend Locke increase the drop rates of the chest?