[RPG] 3.5 Tome of Battle – Warblade maneuver replacement and maneuver prereqs

Quoth ToB, p38:

Initiating stances and manuvers:

... The process of initiating a maneuver is similar to that of casting a spell.. though there are some key differences ...

P39:

Resolving a maneuver or stance:

Many maneuvers include an attack of some kind. All offensive combat actions... all maneuvers that opponents can resist with saving throws or that otherwise harm or hamper subjects can be considered attacks.

...

P42:

Strike: A strike is a maneuver that allows a special attack. Strikes almost always require a standard or full-round action to complete. Many of them involve making a melee attack as part of completing the maneuver. If the attack hits, your opponent normally takes normal melee damage, as well as suffering the effect of the strike. When making a strike, you use your BAB, [and normal modifiers] as normal.

So an example of a normal strike is: "blistering flourish" from desert wind. If you hit, you glow for a minute and creatures nearby need to make a DC 11+wis or be dazzled.

death mark that explodes in a fireball is the same.

Looking at diamond mind, the action before thought counter requires a concentration check in place of a reflex save, no extra attack.

Diamond nightmare blade is the item you described. Unfortunately it looks like case one from the text and as discussed here, you roll concentration to get a 4x multiplier and make your opponent flatfooted. You then have to attack as normal.

You must make a Concentration check as part of this maneuver. The DC of this check is the target creature’s AC. You then make a single melee attack against your target, also as part of the maneuver. If your Concentration check succeeds, this attack deals four times your normal melee damage. If your check fails, your attack is made with a –2 penalty and doesn’t deal any additional damage. If your strike is a critical hit, you stack the multipliers as normal (PH 304).

Functionally this is "roll twice to do OMGWTF damage", which indicates that you should invest both in a very high concentration (or other key skill of the discipline) and a good attack bonus. Given that insightful strike replaces your damage with a concentration check... and the insane ways of boosting skill checks... this doesn't seem like an unreasonable requirement.

Every power describes its use. Most do not "replace" attacks save where they indicate that they do.

The Weapons of Legacy rules are generally considered terrible. If the DM has already committed to them, and the DM's using them as written, a character is often better off not having a weapon of legacy than he is having one. The difficulty of meeting higher-level legacy requirements means that the quests to activate the legacy weapon's next ability can occupy a significant table-time; in exchange for that the character gets the ability to spend a large amount of cash upgrading a weapon that gives him larger and larger penalties to the things he's supposed to be good at. It's... just not very good.

That said, if the DM's house rules make weapons of legacy as good as they're promised, that's something else entirely, and may make the legacy champion class worth taking.

However, in the absence of that, I'd take a build that went warblade 16 (and even consider warblade 20 and taking cross-class ranks in the skill Use Magic Device) instead of any build that takes levels in the prestige class legacy champion if only to avoid having to deal with the deeply flawed rules in Weapons of Legacy.