I assume if you're here then you're struggling with this, but guess what? I'm here to make this easy for you.
Character
Vylat
Passive: Transfusion
Glyph: Royal Blood
Talents
Offensive:
Cryomancy
Alacrity
Torturer
Outburst
Battle Cry
Defensive:
Shockwave
Ironclad
Take A Breather
Guidance Tome
Battle Scars
Max your vampire racial trait if you haven't already and the coagulate glyph, although I don't think it will make or break the run. The familiar we will be using is Jinn because he plays perfectly into the defensive playstyle we'll be using.
Runes:
Winter Rune - Frozen Enemies take more damage
Alacrity Rune - Increase Attack Speed
Power Rune - Increase Damage
Time Rune - Increase Cooldown Reduction
Bargain Rune - Price Reduction at Shops
Now to begin you run. There isn't much to say, the passive and glyph combination will do most of the heavy lifting for you. Your goal is going to be to farm as many HP boosting/defensive skills until the Elites/Mini Bosses start to show up. You'll be going for buffs from the holy weapons such as Priest/Templar/Paladin. Getting these will open up great passives that can further scale your HP to the moon or provide healing to yourself. Once the first Mini-Bosses spawn your goal is to be within range of your Transfusion every 12 seconds when it procs. Every since time you drain a boss you'll increase your HP by 3%, so getting your HP as high as possible before they spawn is integral because it means spending less time dodging lethal damage. When night hits the boss spawning cranks to insane levels, but guess what? We don't see danger anymore, we only see HP increases. So just keep existing near them and ramping your HP up and before long you'll be unkillable with boredom being the only force in this game capable of defeating you.