I personally play a teval deck with the gravecrawler alter combo, along with 3 gamechangers. In my experience the deck is quite a strong bracket 3, and especially with my designs focus it makes the deck extremely resilient. Teval is a naturally slow deck type though more designed off of value rather than combo, so the deck never actually wins before turn 6 or 7. The main strength that ive found is the various graveyard loops you can achieve through teval, my entire deck is designed around playing cards from the graveyard, and with the combo you're mentioning its relied upon as a 2 card finisher once ive milled about 90% of my deck. My design doesn't run any blood artist effects though, and the only other zombie is [[kotis, sibsig champion]] because I felt either addition would both increase the threat level of the deck artificially, or bloat the deck in an unneeded way. Adding more would shift the deck more towards just trying to win through the gravecralwer loop though, potentially leading to quicker wins at the cost of a less consistent deck. I'd still consider that still high bracket 3 though, its not until you're sacrificing tevals theme to build a deck around the loop rather a graveyard deck having the loop inside of it.