Firedancer said:
However, in DnD undead are relatively commonplace, certainly there's a means to combat them (turning, circle of protection) effectively, spells that target them specifically or more effectively. There's means to cure the disease. And quite frankly the zombie as stated out is weak.
If you want to make them scarier, increase their Damage Resistance to 10/slashing and rule that once they reach 0 hit points, they are still "alive" - their limbs might be smashed, but they can still crawl at a speed of 5' per round and they will attempt to bite people.
But I'd caution against making them too individually powerful. That's not their point - any organized group of fighters (even commoners, if they know what they are doing) should be able to deal with them if they are not outnumbered.
The main question is if the living are able to organize themselves fast enough to be overwhelmed by the zombies. After all, if there are enough infected people, both
cure disease spells and turning attempts of the clerics on the scene will run out
fast. And sure, high-level fighters will be able to take out a lot of zombies - but they can't be everywhere at once, and people will be infected faster than they can find and destroy zombies.
Ultimately, to defeat the zombies, humans need:
(a) Good fortifications in which they can regroup. Traditional castles shine here - their whole point is that they serve as "safe points" against outside enemies (although the defenders must keep vigilance against any of the infected infiltrating the castle...). Most cities, on the other hand, are death traps - first the plague will spread like wildfire in the poor neighborhoods and quickly overwhelm the rest.
(b) Good organization. Someone must
always be on alert against new approaching zombies and be able to warn the others - but at the same time, people must be able to continue in their day jobs, or else the fields will fall fallow, equipment won't be replaced, and so forth.
(c) Good morale. Getting bitten by a zombie is essentially a death sentence
unless a cleric is nearby who hasn't expended his
cure disease spells yet (or someone has a potion with this spell effect). Nevertheless, people must be willing to stand up to the zombies and use efficient tactics to defeat them - if they just flee from the zombies, the zombies will eventually win, because they can dedicate 24 hours a day to following and attacking humans.