So, I brought smn/whm to fight Shinny, and I was able to contribute. Here's what I did, if anyone wants to try out or has a better strategy.
1) Talk to everyone ahead of time so they know what you are going to do.
2) As soon as you get in, Perfect Defense the first tank. Not during the brew stage... they're pretty much invincible then. But when the monk runs up and starts tanking. This was a big stress releaver for all people involved.
3) Immediately summon the appropirate element, siphon, dismiss, summon diabolos, use Avatar's Favor and stand by the whm.
4) As soon as Perfect Defense wears off get Dream Shroud on the tank, then run back to the whm to keep the refresh up and start helping to cure.
Best of luck!