That's right, this FAQ was specifically tailored for NIN/RDM|BLM in parties, because that's what the questions were about. It's pretty powerful in solo, but I think better suited for inclusion in a NIN soloing guide (because NIN/WHM is also rocking in its own right).
I did a lot of soloing as NIN/RDM while I was seeking parties, also in Altepa. It's a nice way to practice Ninjutsu timing, and get some easy XP. Some of the elemental katana WS's are actually pretty powerful when you debuff the element, I had a lot of fun using Raiton: Ni to make Blade: Chi hardly ever get resisted.
I am going to have to say that NIN/mage is a great tank given that you are fighting something that doesn't resist too much, or stop you from being able to cast. Crabs, beetles, crawlers, and things like that you can tank very well against. But Spiders, tormas, and things like that are harder. Also it's much better when going against low IT or high VT mobs, as you won't be resisted much.
I tanked in nearly every party I was in from level 40-68, post 60 it gets harder as other jobs get more damage equipment and you start to get resisted more. But if you are the tank in the party you can get another damage dealer instead of a tank.
Keeping hate from provoke shouldn't be hard at all. as the spike from that isn't much compaired to an unresisted NI spell. I know when I have had a thf in my party, I would have to hold back untill he did sa/ta onto me because the provoke wouldn't hold hate. I would turn the mob before they got the sa/ta off.
I don't really understand why people keep saying this, I've tried tanking as NIN/RDM and it always runs into the same problems. First, +INT and +evasion gear are mutually exclusive for the most part, meaning that you have to gut your damage output (and thus your only method of holding hate) in order to get acceptable performance out of your shadows. Second, you have to stop spinning the wheel when you are running out of :Ni shadows, because otherwise you'll ***** up the :Ichi transition. Third, your grip on hate is very loose at the beginning of battles, meaning that the DDs have to hold back almost until the end of the fight, when you actually have accumluated enough hate to keep a WS from stealing it.
I've "tanked" Robber Crabs as NIN/RDM, for example, when they were VT/low IT. DDs with spike damage abilities are my worst nightmare in that scenario, because I have no way to spike hate to compensate for a Barrage/Sidewinder, or a big MB.
PLDs make us look stupid. I've fought with an Elvaan PLD who was not only able to keep hate from me better than 50% of the time, but could keep the mob from looking at the spike DDs without batting an eyelash. There's no way for a NIN/RDM to compete with Flash, Provoke, Shieldbash, and Sentinel. All we have are debuffs, Cure II/III, and :Ni nukes.
I just don't consider it worth the aggravation. Technically you can keep hate most of the time if you have merely average DDs (or DDs with a lot of damage mitigation, like ???/NIN), or a THF to trick a bunch of hate on you every fight, but that still leaves you vulnerable to exceptional circumstances (like links). Bascially, I have to attach so many caveats to it, that it would be irresponsible to suggest NIN/mage "tanking" to anyone but an elite player, or someone with an understanding static.