Clerics get as many spells as a specialist wizard, know all the spells on their spell list, have healing magic, better self combat buffs, some more powerful divinations, they only fall behind on straight zaps. In addition their HD is twice as big, they get medium BAB, strong fort saves, heavy armor making them much more sturdy than a wizard.
With their decent HD and BAB plus their heavy armor and buffs they can make decent front line warriors, focused on magical self buffing they are stronger than a warrior for the time they are buffed.
Plus they get turning as a bonus and domain powers.
With diplomacy as a maxed out class skill they can even play a decent face man role.
Their detect traps spell lets them play a little bit in the trap detection.
So their weakness is dodging and scouting, but they can do most everything else, and do it pretty well.
