One of the best epics I ever made was this combination of Bardsong and devastating critical plus a good naked AC and immunityes of a Red Dragon Dissiple. The beguinning atributes where: STR16 to 28 DEX12 to 12 CON14 to 23 INT12 to 12 WIS10 to 10 CAR10 to 12 and a focus on the rapier to have critical hits more often and a higguer chance of Devastating Critical. The AB with a non magical rapier is: 45/40/35/30. And good saving trhows: FORT30 REFL24 WILL27 and a list of immunityes due to the Red Dragon Dissiple class, as well as a breath weapon of a lv10 RDD. The hitpoints are strong as well, with a total of 345 or more if the hit dices are high. One of the only weaknesses of the Dragoon Cavalier is his low rank on spot and listen, which makes him a little weak against sneak attaks,but the ranks he has are enough to detect low level rougues. I am not posting my entire build here YET because it need more testing, but it is showing out to be a grat build for these that don't have patiebce using buffing spells or complicated tactics.
taking another bard at level 40 allows max tumble AC..
EDIT also could you not skim rdd10 at level 39 or 40 to max listen/spot?