Cards with unique abilities are always hard to judge at first glance, so there's sure to be some other interesting ways that Senu surprises all of us.
If I recall correctly, this began in the core set with Garruk, Primal Hunter with a rough five-cost with triple Green, but then +1 to make a 3/3 Beast that's Green or -3 once to draw
Atog Atog | Illustration by Jesper Myrfors This one is for my son, who avoided saying yes to learning Magic with me for a year when he was younger because he saw this red card, recoiled, and peaced out
If it was a circle then the card was common
In general, I would look at these two factors when looking to include cards not of your tribe's creature type: Is this creature so strong that it, on its own, is generally stronger than my tribal creatures when they are receiving bonuses and/or empowering my other cards
I'm glad now that I have some distance from my job because I've realized that an important part of what I do (as a creative endeavor) is allow things to percolate