Say, what is the first thing that comes to mind when you talk about Tome of Battle? Most likely, the maneuvers – the thing that made the close-quarter combat fun for even those players who don't like to just smash things with a metal stick 'till it breaks. These maneuvers are so awesome that a 1-level dip or the Martial Study feat are really good options just to cherry-pick some stuff to give a non-ToB PC another level of badassery. They are just smoking burning rad, and that's the fact.
Then, we take a look at PrCs. Some of them are weird in fluffy part, some of them need you to be, let's say, an elf… And some of them make you drop the latter half of your maneuver progression while giving you mediocre to weak character options (yeah, I'm talking about that weird Shadow Sun Ninja). Pretty much the only PrC that doesn't require your character to be a battle psycho, a pointy-eared or heavy-bearded guy, or to multiclass/give up on maneuvers is the Master of Nine.
But looking at the PrC Tiers list it looks like the Master of Nine is the worst ToB PrC to take (-1 Tier, which is hard), while weird, not very useful and easy-to-almost-fully-replace-with-a-"+1LA"-Template Shadow Sun Ninja gets a "+1 Tier" for… I don't know what.
As far as I understand, the Maneuvers are the most valuable resource in ToB (the second one are Stances, which are nearly as cool), and high-level maneuvers are nearly unobtainable without being a dedicated martial adept. Getting not-too-hard-to-resist abilities of being a light show at-will? I don't know, but even getting an ability "to burn a small village or an army every 12 seconds" sounds better to me, not to mention ability "to pick maneuvers and stances from ANY of the Nine Schools" which Master of Nine gets. But maybe, I don't understand something?
So, here's the question: Why is it a bad idea to get the Master of Nine PrC? Is it really not worth those admitably not-very-nice (Dodge? Yeeah, riight…) prereqs? What makes it not worth the efforts?
Best Answer
First of all, the Prestige Class Tier List is not nearly as widely-ascribed-to as JaronK’s base class one. For one thing, it is much harder to judge a prestige class (especially ones that can vary so much depending on how you enter), and for another there are just so many more of them.
Take the Shadowsun Ninja. For a Monk, it’s a dramatic step up; for a Swordsage, it’s... a thing. There are some neat tricks possible with it (Tomb-Tainted Soul or the Undead type allow you to use the negative energy for healing while using the positive energy on your allies, so that’s indefinite healing), but ultimately it doesn’t really change much about the Swordsage’s tier.
The problem of the Master of Nine is that it requires a ton of feats. If you aren’t a Swordsage, it also requires multiclassing, but that’s not really a bad thing for initiators. In fact, judicious multiclassing helps a great deal with the feats, because one level in Cleric gets you two of the feats (Darkness or Shadow domain gets Blind-fight, Time domain gets you Improved Initiative). The unarmed Swordsage adaptation also gets you Improved Unarmed Strike, and most Swordsages want Adaptive Style anyway.
That leaves only Dodge to be picked up. Several options, including Tome of Battle’s own Desert Wind Dodge, are better than ordinary Dodge, though even the best is still weak. Still, one feat burned and the single-best-dip-in-the-game (don’t forget that Cleric 1 also gives a few spells, and Turn Undead can be used to fuel the often-excellent [Divine] and [Domain] feats) is not too high a price to pay for the excellent class features that Master of Nine offers.
The limited Dual Stance feature is not nearly as good as the Warblade’s version of the same, but it’s still awesome and you can get it way sooner than 20th level. The eight maneuvers in five levels, of course, is phenomenal, and a maneuver readied per level is insane.
If you try to get into Master of Nine as a regular, single-classed Swordsage, you’re making a huge mistake and will regret burning all of your feats that way. If you’re clever about picking up feats, though... the class can be excellent.
Side-note: you don’t lose “more” by taking another level in addition to Cleric 1 with your Swordsage levels, because other class levels count half for your initiator level. There are a lot of great options for that extra level. Fighter or Psychic Warrior could be used to get another feat, to make up for the one lost picking up (Desert Wind) Dodge. Psychic Warrior also grants you a single power – which could be expansion, for instance, a great choice. Barbarian gives a ton of stuff on level 1 as well (don’t forget to check the various alternatives for Rage for the one that best works for you).