I am not sure what version cubecraft is on. I believe it is actually 1.8 and 1.9, and the 1.9 version has compatibility with 1.10 and 1.11. If I am correct, there cannot possibly be totems of undying as the item is only in 1.11 and above.
If they could add it, though, it would be quite redundant. Notch apples do almost the same thing, keeping the player alive when they should be dead. Totems of undying are not extremely overpowered, but they are overpowered enough that I do not believe they should be added into the game. However, I am not extremely against adding it, since it would not change the gameplay too much if they are correctly implemented.
If they are added, they should not cost emeralds. Emerald generators are on very few maps, and they are not really balanced. I would suggest making totems of undying cost 1 - 2 stacks of diamonds (did no one ever notice that you can have a primary and secondary trade item with villagers?). That way it is accessible, but not overly so. It is overpowered, but within (just barely) the range that I accept.