Managing your own aggro can help a lot specially if you are dealing with a low gear Tank, indeed.
As of late I've ended as a NIN tank for CT2 last boss more often than not simply because the Tanks can't keep up :/

Needless to say that never ends well...

But it not only applies to yourself, it seems you can also lower your allies' Aggro... *throws it to the Tank* now the Healer is the Tank!!
Well, TrollNIN is underway.