But in D&D if you're not running, you can just make a longbow full-attack anyhow, and get the same number of arrows-per-round without using a Manyshot feat.
The full attack is at -0, -5, -10, -15, for an average of -7.5 attack, while the Manyshot is at -8, -8, -8, -8, for an average of -8 attack. Therefore, D&D characters don't even gain DPS from manyshot unless they were planning to move while fighting.
PS. The word to rest an arrow on a bowstring and prepare to shoot is spelled "nock".