your unit combination is bad!
:>
bowmen are really bad ranged units due to their high leadership cost and damage they do
priest are pretty useless vs living units
you should take
horseman/royal snakes
inqi's
alchemist(their potions rocks and they are garantueed although not alot of people like them due to their relative high leadership)
evil beholders(mind control owns, and their sleeping ray is also very nice)
for the last unit u can take anyone i mostly try to get a shaman from the inn on arlania if ain't getting that i ussualy restart my game
shamans are masters of killing bosses
especially with phantom you own any boss with any combination ^^(so long there is at least 1 ranged unit xD)
and if your an undead leader
use ancient vamps
normal vamps
cursed ghost
skellie archers
ghost
simple as that
any other unit i would not recommend
but then again it's your choice