To wear down players, your werewolves don't have to fight. They just have to make the PCs think they're about to fight.
The PCs are basically leading a retreat. They have tired, worn-out, non-combatants who need rest and who are slowing down the movement.
The savvy enemy works WITH this weakness rather than pushing against it.
- During the day's walk, wait until the entire movement has ground to a halt for a rest. Have a member of the werewolves howl somewhere in the distance -- to far away to risk rushing out for a battle, but close enough to keep everyone on edge. Never directly engage the enemy, but always keep them on their toes.
- At night, wait until the noncombatants have had plenty of time to get to sleep. The make a great deal of noise somewhere close enough to rouse the group. Fade into darkness. Again, don't engage, just rouse. This has the added benefit of disrupting your spellcasters' required 8 hours of rest, if they can disrupt often enough for long enough. Plus anyone who needs sleep is going to be exhausted from sleep deprivation. Sleepy people make mistakes and get grouchy.
- Keep vigilant. If the group ever starts fighting internally, due to sleep-deprivation and frustration, go in for an attack at the fringes, never directly. Pick off one civilian at the edge of camp. Maybe the guy who storms off in a huff, or the guy who wants to stay away from the arguments. He dies and there's no trace of his body. Opportunistic feeding / attacking is low-risk and high reward for driving up the psychological warfare angle. Maybe leave a body part or two, just to prove something bad is out there.
- Never get caught. always stay one step away from them. If they try to scout out your location, fade into the wilderness and regroup elsewhere. Keep them under surveillance so the PCs never get the drop on you.
- Seek advantage. If you can capture a civilian, do so. Learn what you can if you're able. Otherwise, torture for effect. The distant screams of a village elder can be quite motivating to your villagers.
All of the above, night after night, day after day, will result in spellcasters who have no spells, NPCs who are at each others' figurative throats, and a worn out group of travelers who cannot hope to make good time towards the village.
Play this up like the first act in a horror film, where stuff keeps happening, but the players never quite see it happen directly in front of them. The mystery will fuel the fires of fear: how many combatants do we face? How tough are they? What are they?
If they panic, the NPCs will certainly panic. And even if they don't, the NPCs might panic anyway, say after a particularly grisly attack happens just out of sight. Panicked people are prone to particularly poor decision-making practices. Use that to further ramp up the terror and worry and fear.
Fear is a self-feeding flame.
The werewolves aren't stupid. They know that a full-on frontal attack could well be suicide. But guerrilla combat techniques let them maintain the initiative (er, not the dice-based initiative, though if they're always sniping from surprise...). They aren't going to get trapped, because they know the terrain and are better equipped for this kind of fight.
The above concepts are basically worked out from years of playing and trying to get into the minds of the NPCs rather than looking at the game as a tactical combat board game.
How would reasonably intelligent foes go about their goals? Do they have goals? They should have goals or they're just raging chaos-monsters in a board game.
So see the scenario through their eyes rather than through the GM's all-seeing eyes. They see an enemy trying to sneak out of their territory after having done bad things. They simply must be punished; that's the law of the pack. So how?
They're not stupid, so they know wading in directly and fighting isn't smart. They have magic and swords; they might win and even if they don't they might weaken the pack too much for survival to be assured.
So that's when they get sneaky.
In my experience, both as player and as GM, "how should I deal with this situation" has many potential answers, but when you treat it as "how would this NPC/these NPCs react to this information or situation" then the responses feel less like generic plot points on a story arc and more like realistic events to roleplay with. And really, that's what works best.
I've never had to deal with werewolves hunting PCs -- from either side of the GM's screen. But I have dealt with long marches, PCs having to escape an unseen foe, and trying not to get caught out in a fight. And those events tend to be far more memorable than any combat encounter.
The best example that comes readily to mind was a mass combat at a convention where two teams went head to head (about 20-30 PCs total). Side A's goal was to capture or kill a child because she was politically important (a princess, or the daughter of an important person?). Side B's goal was to save her or secure her escape. So the fighting raged on for a long time and that was cool and all, but it was just dice; just fighting. But the last four rounds or so? That was when Side B realized they didn't have enough surviving people to secure victory. "RUN!" they yelled to the little girl. She ran. Side A went for a full charge, hoping to capture the girl or hit her with an arrow. Side B stood their ground, trying to save her. They died. To the last man on the field, Side B was wiped out. But their sacrifice secured the girl's escape. So while they all died, they won.
And that? That was memorable. Not for the fighting. But for the sudden shift in goals. The goal wasn't winning the combat round. The goal was that NPC girl and her effort to run.
So yeah. Shift focus. That's what can make a game memorable.