Pat the pork tenderloins dry. Stir together the salt, pepper, garlic powder, onion powder, and smoked paprika, and rub all over the pork.
Heat the olive oil in a large skillet over medium-high. Sear the tenderloins on all sides until deeply browned, about 6 minutes total.
In the slow cooker, whisk together the minced garlic, chicken broth, soy sauce, Worcestershire, honey, and Dijon. Nestle in the seared pork, dot with butter, and add the rosemary and thyme.
Cover and cook on LOW for about 3 hours, until the pork reaches an internal temperature of 145°F.
Transfer the pork to a cutting board and tent with foil to rest for 10 minutes.
Whisk the cornstarch and cold water into a slurry. Discard the herb sprigs, stir the slurry into the liquid in the slow cooker, and let it thicken into a gravy.
Slice the pork against the grain and spoon the gravy over the top.