Well, in fact, you are missing out on several things.
1) ->Steely Resolve progression
Steely resolve is simply amazing, allowing you to soak up damage and return it with interest. Four levels of crusader lead to steely resolve 10, which is *a lot*.
Combined with Stone Power, you can effectively gain *FAST HEALING* 8 at level 4, and 10 at level 5, assuming you take that much damage in melee.
2) -> Initiator level, fast maneuver progression, stances.
Crusader's strike scales with your initiator level. The same can be said of many other strikes and stances.
Taking Crusader levels is the fastest way to learn more maneuvers, to expand your range of known/granted/readied maneuvers and available stances, ultimately leading to more versatility and staying power.
A 3rd level crusader can take Mountain Hammer as maneuever and tunnel through stone walls in the WLD with his bare fists if he needs to, digging around traps, obstacles, etc...
A 5th level crusader gets White Raven Tactics, which is immensely powerful.
3) ->Defensive Class features
At 2nd level, Crusaders get Cha to Will saves. This isn't much, and probably won't do anything if you dumped cha, but the option is there.
More importantly, at 3rd level, Crusaders can reroll a failed save once per day. THAT is really, really useful.
4) ->Energizer Bunny traits: Crusaders, unlike Psychic warriors, do not have a finite supply of powerpoints. They can continue to use and reuse their maneuvers over and over and over again, as many times as the situation requires it.