The Bloodstalker is a game-changer in the Genesis dlc since it is the fastest way to get across most maps without fliers. They are relatively easy to tame, you just need to craft a syringe and make lots and lots of blood packs. It might be helpful for you to also have a preserving bin to store the blood packs in. Then you need to find the bloodstalkers. They hang out in the massive trees in the bog biome.
I have found them at the following locations:
After you find one, put your blood packs in the far right slot of your hot bar ("0" slot on PC). Get underneath the bloodstalker. If you are close enough it will send out a web and drag you to it. Then the bloodstalker starts feeding your blood packs instead of you! Taming the bloodstalker doesn't take a lot of time, but it can take a lot of blood packs. As I write the game hasn't been out long and people say it takes a lot of packs, maybe a 100 or more to tame a high level.
With my slightly boosted rates it took a short while and 12 packs to tame a level 20 bloodstalker. Good luck taming a blood stalker, or should I say getting enough blood packs, either way, once you get one of these creatures the new Genesis dlc will get much easier, but it will still be hard.