As blu I have tanked Tia and Cerb, and used no - dmg gear other than earth staff. I dont bother with Macuahuitl at all. Actinic burst is max hasted and treated like i treat my flash on PLD same with blank gaze (good hate tool, and dispel lands on tia), I spam jettatura whenever its up (it very occasionally terrorizes Cerb), temporal shift whenever on cerb but saved for touchdown on tia (always stuns), and i toss exhuviation out occasionally but rarely need to diffusion exhuviation as I wouldn't be able to get the mob off me defeating the purpose of sharing hate with a cotank. I have a macro that does CA BA Convergence one after another for a little Enmity boost. As long as nothing in the area to catch with AoE blu is much like a pld but with the rdm spamming of the spells (but can do HP - + sets with magic fruit much like a pld also).
http://i44.tinypic.com/2s67cw0.png
Tiamat aerial shot. Pretty standard dmg reduction from fire resist this shot was before I had some fire gear that I have now. Saline Coat and Cocoon in the shot are not necessary at all ever this was an early test and the spells really have no use except for saline on ultima.
You honestly can generate as much enmity as you could possibly want, I don't really run out of MP and would do so less now with AF2 body. (I could care less about the -2 enmity on it as I was initially tanking with hardly any enmity gear). There are some advantageous job traits that you get with blu over PLD including mdb, conserve mp, auto-regen and I love the fact that temporal shift stuns and blank gaze dispels, you also get some additional haste that PLD doesnt have access to in Nashira body.
I have 75 PLD and would much rather tank something on blu because I feel I can generate significantly more hate, I imagine this is what a player with a nin/drk and pld/nin feels like as well. Just as long as nothing is in the way blu should be able to tank whatever.
Edit: To add, some of the people in this post have suggested head butt, other blu stun spells, and even other phys blu spells. I would strongly and I mean very strongly advocate not doing phys spells ever for obvious TP reasons.