If C.Adv. is available, every melee rogue should have
Staggering Strike. No exceptions. If Champions of Ruin is available, every Rogue should take
Craven. Note the damage is based on character level, not class leel, so being multiclass doesn't hurt you.
And ditto on the suggestion of Penetrating Strike alternate class feature. You may also want to look at Dungeoncrasher Fighter alternate class feature (ACF), also from dungeonscape. Works best with a Goliath and the knockback feat, though. Also of interest is the Zhentarim Fighter ACF, which is available as a free pdf supplement online from WotC's website. It literally just gives you freebies. All related to demoralizing and intimidating, if you're into that. Note that with charisma 15, you can qualify for
Imperious Command (can't find the full text online, but that table entry basically covers how it works), which is an AMAZING feat. Which you could combine with things like
Intimidating Strike. And/or the Never Outnumbered skill trick from C.Scoundrel. For the price of 2 skill points, lets you demoralize all foes within 10 ft when you demoralize someone, so with a reach weapon and Enlarge Person, you could Intimidating Strike someone 20 ft away and intimidate everyone around you as well, and leave them all cowering. I did this before, it's very fun, although setting it up is a little on the suicidal side.
EDIT: Drow of the Underdark also has the Hit and Run ACF for Fighter, which is great for fighter/rogues. Lose some armor proficiencies for an initiative bonus and the ability to add dex to damage against flatfooted enemies.