Going by what people have told me I parse.
Last time I killed t6/7 on my alt blm (i97) I did 328 on t6 and 308 on T7.
On my main i105 blm I did 350 on T6 (think my best so far) and can't remember what people said for t7/t8.
1 Bard in each party, though Foes usually only on pull. First time doing t6/t7 with that team on my alt.
Realistically I'd say you should be aiming at 250+ on T6 and T7 and 320+ on T8, to be pulling your weight as a dps. Any higher is just a bonus.
