By Lakshmi.Byrth 2011-02-23 19:34:14
I think awesome NINs are better tanks on average than awesome Dancers. Furthermore, there's only one fight I can think of that Dancer is better equipped to tank than Ninja, Emperador de Altepa lowman. If you want to claim Dancer is a better tank, you need to invoke DD reasons.
You can start off by assuming NIN is subbing Dancer, because it simplifies the comparison (gives many of the same JAs, gives NIN more evasion, etc) and they wouldn't sub anything else unless it was even better for tanking.
Ninja - More evasion and Attack than Dancer, feeds less TP thanks to the Inhibit TP Ninjutsu, has Migawari, has an easy and powerful PDT set if required. Has Blade: Hi.
Dancer - Has access to Fan Dance, Has access to Saber Dance, has 5% more Haste with their Haste Samba. Probably has more Accuracy than Ninja. Has Rudra's Storm.
In a Tanking situation (not a solo situation or a "I'm duoing with my Black mage mule" situation), any amount of damage doesn't matter unless it kills you, because your white mage is sitting there with their finger on the Cure 5/6 button. This means that Fan Dance is essentially a one-shot prevention mechanism that only works for physical moves. Because Ninja also gets a one-shot prevention mechanism (Migawari), this means that Fan Dance is really only superior if you expect the one-shot move to be spammed (Ex. Emperador).
Dancer may be a better DD if you just have Haste and can ride Saber Dance. Blade: Hi is a relatively large obstacle to overcome though.
Dancer's main advantage isn't very intuitive. Because of the way hate works, the person who caps hate most recently ends up tanking. For instance, if your Black Mage nukes for 6000 damage and you already have capped VE and CE, re-capping your hate with a single attack round will pull hate back off the Black Mage. Dancer has more frequent Attack rounds than Ninja (lower delay weapons), so they are slightly better at holding hate once they've capped it. If you have a Dancer and a Ninja tanking a monster, after they cap hate the monster will probably spend more time swinging at the Dancer, etc.