i am not familiar with the wc buffs, so is it possible to have wc + pp buffs at same time or will one overbuff the other?
for example, is it possible to have haste2 + chant of fury in order to have a higher atk speed than with only haste2?
no, wc buffs and prophet buffs will overwrite each other if they buff the same stat. there are some buffs that prophets have over warcriers and vice versa( windwalk or chant of evasion), so it would be beneficial to have both in the party. Prophets also get higher lvls of the "same" buffs on lower levels than warcriers.