Well at low-levels (and at the higher levels), the WB outstrip the fighter simply because the Ftr doesn't really gain any benefits from full attack (except in a few rare circumstances, such as a TWF Ftr) because he doesn't yet have iterative attacks. In fact, level five and below is the best opportunity to make use of single attacks, such as Spring Attack, which won't get as much mileage at say, 16th level. And yes, "recharging" your maneuvers is cheap at level 5 and below (since Ftr's don't have swift actions to spend on) but you're going to feel it in the higher levels.
As for your 1d20+17 damage, as pointed out by Slaved, you're sacrificing potential attack/damage bonus (since your main stat is now Con instead of Str) and you're relying on that one maneuver instead of overall effectiveness. I'd also like to point out that Insightful Strike is a level 3 maneuver, meaning the character just got it at 5th level and is at it's "most optimum level". I mean if we bump the character's level by one, we'd have either a Ftr 6 or a WB 6, with a base attack of +6/+1 plus whatever modifiers. You have two attacks if you made a full attack and let's assume you're wielding a +1 greatsword and have a strength of 20 (18 base Str, +2 enhancement from a magic item). Your potential damage in each instance is 2d6+8. So now it becomes a 1d20+18 damage vs 4d6+16 (and a higher crit threat range). Granted, both attacks must hit in order to achieve that number, but then again, you also have a higher Str because your stats went to Str instead of Con. And as pointed out, it's a good chunk of investment in feats on the Warblade's part (and he doesn't have lots of those) while the Ftr hasn't spent any in this calculation. Theoretically if he spent two feats on Weapon Focus and Weapon Spec., his attack bonus in each instance will go up to 1, and the damage potential would now be 4d6+20. Not that I'm saying this will always be the result (since as many people pointed out, you won't always get a full attack), but I think we must also accept into our equation that full attacks will occur, and Ftrs want that situation to happen. Of course the WB focusing on the Insightful Strike maneuver tree will be less item dependent (which is both a strength and a weakness, because on one hand, it makes no distinction if you're using an unarmed strike but on the other hand, doesn't benefit you if you're using this colossal +5 greathammer), but at higher levels, Ftrs theoretically should be getting better gear and magic weapons, which the Insightful Strike maneuver tree doesn't really benefit from.
Oh, as for the Diamond Mind counters (the Will save and Ref save you're talking about), that has its own limitations as well. Theoretically you have achieve higher saves, yes, but you must realize that 1) they're immediate actions, which means that's one swift action (usually a boost) that's unavailble to you on your next turn, 2) you're spending a maneuver, which means you might not have access to it again until you "recharge", and 3) doesn't help you against multiple saves in a round since it'll only work once. It might help against the first fireball in the round, but it won't help against the second. Not that the Ftr is in a better position, mind you, but that's one of those days that I'm glad I'm a Paladin and not a Warblade.
And I also mentioned gishes because certain gishes also have a certain sweet spot on certain levels. Take the Duskblade: at 5th level, thanks to Arcane channeling, I can deal my melee damage +5d6 electricity damage (shocking grasp) as a standard action thanks to Arcane Channeling. Granted, I can only do it 5/day minimum and not the infinite potential of martial adepts, but that depends on the encounters your GM throws at you, in the same way that a Warlock will earn his keep if the GM throws 10 encounters/day at players, while the Psion will seem more powerful compared to the Wizard if your GM just has 1 encounter/day.
