Depending on your deck, this might be fairly useful. In some more dedicated builds, it'll essentially say "Put a +1/+1 counter on each creature you control". I don't think many of those decks will exist outside casual, but some cards are just meh but decent in casual circles.
If nothing else, it'll be good in limited where you'll usually have a monster to toss a counter on and grow since a good portion of the creatures aren't Humans. It's a low pick, but it has some uses.
Today's mothership article suggests that it follows the pattern of the bonder and rare ally cycles, except for the black one, which grants lifelink instead of flash.
W - vigilance
U - flying
B - lifelink
R - menace
G - trample
Red is first strike my lad
Given that that the cycle you're citing has Splendor Mare as the white representative, and we can clearly see that the white mentor doesn't align with the lifelink that cycler grants... It seems likely that those two cycles are not perfectly aligned, and we should probably go with what Wizards themselves have said about it, since they probably have more info than you.