I know what you mean, the first time I tried HoW I got slaughtered by the first band of barrow wights
A lot will depend on your party and weapons. First thing I did was buy "Three Doves" as it has a % chance of destroying undead outright.
I found by blundering around I was fighting more than I had too at a time. Careful sneaking helps you to discover the enemy first and plan an attack. I prefer an offensive-defense. Lure the Wights out with a tank or archer (whom will then be targetted) then withdraw to a defensive line. You may have to bolster your party with defensive spells (defensive harmony, protection from evil, prayer) or potions (strength, agility, speed). Mages can cast offensive spells from the rear (acid arrow, magic missile, fireaball).
The important thing is to concentrate your efforts. If you "pair off" against the enemy you will suffer. If you can have one or two tanked characters occupy the bulk of the enemies, you can concentrate 4 or 5 others against a single enemy, take that enemy out then move on to the next. That way, the mass fighting your tanks will dwindle and become less effective.
What is your party compostion (classes, weapons etc.)?