In another world, Arthur is number one on this list for being a core piece of that deck - but he just doesn't cut it
All that being said, Gideon Blackblade doesnt really fit in competitively
As for the best of the new creatures, O'aka, Traveling Merchant turns your excess counters into carddraw, and Maester Seymour grows creatures of your choice as you grow him
Vivi can only be used be turn and only your turn , so you won't be able to have excess mana to work with on your opponents' turns
Cards like Ohran Frostfang, Saryth, the Viper's Fang and All-Out Assault dont have deathtouch, but they thrive on giving your creatures deathtouch when you attack
Its a big threat thats hard to block and it deals a ton of damage when it dies