There are only a few enemies that reflect a lot of damage in the game, and you can just be careful around them. You can recognise them by their title (reflective) for heroes, the specific enemy type in general (certain skeletons, possessed archmages) and the yellow glowy shield thingie they have on them. Or just stop hitting enemies when you notice you are taking a lot of damage. The shield is temporary, and when it goes down you can kill them safely.
Normal resistances help against reflected damage. This is a cold damage build, so the basic cold damage resistance applies and reduces all damage by 80%. That makes it manageable without special reflect resistance.
Reflected damage resistance is needed mostly when you are dealing a damage type you do not resist well, and especially when that is damage-over-time. (Because then by the time you stop hitting the enemy, it might be too late. The DoT will kill you.)
In practical terms, this means physical damage characters and especially internal trauma dealing characters need reflect resist. Characters with very powerful long duration DoT effects like Bleed might also need some. But for other characters like this one, reflect resistance is a low priority as long as you are careful.
Just don’t use Shadow Strike to hit an enemy with a reflect shield up, as that is a huge single damage hit and can be dangerous.
