I hate longbows! Being on the receiving end that is.
Even with tower shield troops you lose men with every volley when the arrows are wind guided and fire enchanted (as Shovah wrote). The only relief is that those longbowmen don't have a lot of armor and most new players tend to ignore protecting them from counter archery/"crossbowery" and fliers. Oh, and you can always cast storm/rain/mist (if you're lucky Man will do it for you), that will keep you somewhat alive.