Master of Nine is a very weak PrC. The benefits are top notch (for a BSF), but the feat requirements utterly outweigh them. Even in a gestalt build it takes up more resources than it provides.
Not so. Adaptive style is useful at low levels involving being a swordsage, and dodge and improved unarmed strike can be had for a very inexpensive 1 level in Cobra Strike Monk, allowing you to dump dex, if you want. That leaves Blind Fight, which is situationally sort of handy, and Improved Initiative, which is a generally good feat. Now, for those 3 feats you actually use up, 2 of which are useful, you get 8 maneuvers known, 5 maneuvers READIED, and 2 stances, all from ANY discipline. It's PAINFULLY easy to meet the requirements of maneuvers when you have 2 or 3 initiator classes. Add those maneuvers onto your Crusader levels, and you'll be able to ready 11 or so maneuvers, and get 9 of them granted, which makes it very easy to beam spam with stuff like Time Stands Still (gotten by taking the low level Diamond Mind maneuvers on your warblade dip), Five Shadow Creeping Ice Enervation Strike (swordsage), Tornado Throw(swordsage)... ALL recovered every 3 turns, if you want.
As long as your Crusader initiator level is high enough and you meet the requisite number of maneuvers known, you can put ANY maneuver on your crusader recovery mechanic, and spam them all day long.
Don't even include the tasty dual stances for stuff like Thicket of Blades + Martial Spirit + Stone Power for 20 or more points of damage soak per turn, for tanking things, or Iron Guard's Glare + Pearl of Black Doubt for making your allies and yourself hard as hell to hit. Or the nice Mastery of Nine ability for +14 on all damage rolls you make as part of a Time Stands Still or a Tornado Throw. No, just ignore those.
Still a very weak prestige class?
Ruby Knight Vindicator is
disgustingly good. Multiple Travel Devotions per turn? Multiple counters per turn? Multiple DMM quickened spells per turn? Even if it's eratta'd to 1/round (it was, but I think it's bunk), it's still really fucking good.
Also, at-will cleric casting and divine metamagic options along with CHARISMA based spellcasting is clearly no lower than tier 1. Problem is, it's only available at levels 16 plus without cheese.