The most dangerous part of the swamp isn't the abominations its the clusters of dead body piles and bone piles that spawn an infinite number of draugrs and skeletons when aggroed.

If you see a cluster of stones in a circle-like structure then they probably contain them. They are often close to crypts. You can also use your ears to listen for the insect whine like when you are close to a beehive for the dead body piles. Those are a sickly green color and should be targeted first.

Try to see them before you aggro them and use a bow to destroy them at range. If you have aggroed them and you can't wade through the enemies to destroy the pile itself, just run away as fast as you can out of the swamp. Never attempt clearing them at night if you don't want two or three wraiths hearing the commotion and coming to crash your party.

Until you get your gear upgraded, absolutely run if a 2 star elite draugr spawns and be prepared to use a stamina mead. I had one chase me deep, deep into the meadows and kill me because it spawned when I was low on stamina and couldn't sprint. Every hit I parried took what little stamina I could gain from walking away. Eventually, I made a mistake and died. To put this in perspective, I have T4 iron weapons and T4 root gear and I still get really nervous around 2 star elite draugrs.

Also be aware that clusters can spawn close to each other and if you aggro more than one cluster you will likely die.