I think they do affect glancing blows. Ive seen on my paladin the Divine favor seems to go onto them, as well as songs. When i boost damage to the max<50+ on normal hits> that his glancing blows are for about 24, but my strength is also boosted in that state, so its up in the air whats actually causing it.
TWF is good for aggro management, which is why i love it on my barbarian. Kill one target extremely quickly without always drawing additional aggro. Though on the bard, it doesnt seem to really matter with the smattering of CC i have to use. Fear is great for just thining the ranks, without always stopping all of the melee dps. Because with the Torc on, endless mana is just an orges club away!