Just got this tonight. Went there with 2 PTs, both won.
My PT was NIN, MNK, WHM, RDM, BLM, SMN.
Other PT was...I forget, but they had 2 BLMs.
Both were conventional setups, rather than manaburn style.
Things I noticed about Diabolos was that he sucks at melee. Don't worry about evasion, etc. since he's a pansy in that respect. Just worry about the fact that he spams moves non-stop. He's on a constant Meikyo Shisui or something.
I was the SMN, and did Earthen Ward at the start, which held up through his first Nightmare, but when I tried to use Earthen Ward again, I kept getting slept by Sleepga II or Nightmare before I could make Titan do it again, so I ended up not doing much during the fight other than some Curaga II spamming near the end after his 2hour (which he used at about 25% health for us).
The other thing I noticed about Diabolos was that (when playing with him after the fight) he sucks at DD. His 70 BP Nether Blast did 500 damage to a too weak. He also did 500 to a decent challenge. Granted, its above Rush in effectiveness, but still... he's not going to be a DD avatar unless he also does 500 consistently on HNMs too.
His 2hour did like 5%-10% damage to random DC/EM mobs, which also wasn't that impressive, but maybe it'll be good on mobs with really high HP or something. His Nightmare was fun, but took like 15 seconds to get a dolphin in sea down 1% health. Though you can dia/bio stuff for fun and still have them sleep.
His MAB/MAD boost pact (Dream Shroud) did seem to boost magic damage, but didn't test it all that much so not sure just how much of an impact it has overall. e.g. first test was 971 Thunder IV -> 1130 Thunder IV by one BLM on a dolphin, with and without Dream Shroud. Next test was another BLM's 912 Thunder IV -> 980 Thunder IV on another dolphin (mouth closed on these tests). But that's about all the testing we did on that, so it could just be the random damage variance talking.
The rest of our testing was just beating up on poor mandragoras outside windurst with a team of 6 Diabolos (SMN and /SMN).
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