Mentor of the Meek allowed you to pay 1 mana to draw a card whenever a creature with power 2 or less enters the battlefield under your control. The Bishop requires that you can a creature with a converted mana cost of 3 or less to get a Clue artifact. It’s still a pretty powerful ability. Being a 2 / 3 flyer is certainly relevant, too. This is a card that only gets better as you cast multiple copies. Any sort of easily accessible card advantage, especially in a deck built around smaller creatures, is most welcome.
With the existence of Collected Company, it’s understandable why they wouldn’t want to create a functional reprint of Mentor of the Meek. This is why Investigate only triggers when you actually cast a creature, rather than just when it enters the battlefield. Collected Company decks would happily run a copy to get some Clues were that the case. Alas, the cast trigger is required. In Standard, there could well be decks that run multiple copies of the Bishop. It all depends on how good Clues really are. Outside of Standard, the other Constructed formats probably will find Investigate a bit too slow of a mechanic for competitive play.
In Commander, the Bishop is a bit more limited than Mentor of the Meek. Take for example one of the more popular Commanders from Oath of the Gatewatch, Ayli, Eternal Pilgrim. While the Bishop seems perfect for a Cleric Tribal deck like Ayli’s, many creatures in Ayli’s deck are 4 mana or higher. However, many of those 4-mana creatures have power 2 or less, making them perfect companions for Mentor of the Meek. That said Bygone Bishop could still benefit from the 1-3 drops in the deck, including Ayli herself.
In a Blue/White Spirit Tribal EDH deck, such as one led by Geist of Saint Traft, Bygone Bishop can pair with another Spirit friend, Erdwal Illuminator. This 1 / 3 Spirit creature allows you to investigate an additional time each time you would investigate. Being a 3-drop itself, the Illuminator will let you investigate upon its entrance, as well. Also, most creatures that see play in a Geist of Saint Traft deck are converted mana cost 3 or less, so that’s a lot of investigating that the Bishop can do!
There are plenty of other decks that could use the Bishop, though. Really, that's any Commander deck that plays a fair amount of 3 CMC or less creatures. One Commander that comes to mind that can also benefit from the Clues themselves is Jor Kadeen, the Prevailer. While he himself costs 5 mana (3RW), his deck plays many 1-3 drops. With his Metalcraft ability, you only need to make 3 Clues before his Metalcraft ability activates. Then all of your creatures gain +3/+0. The deck also lacks consistent draw power, so having the Clues around later to draw a card is also welcome.
Overall, Bygone Bishop is a new take on the idea of Mentor of the Meek. It may not be quite as versatile, as it doesn’t trigger on tokens or other small creatures entering the battlefield. But this is a good, well-designed card that could see play in the right deck. It will also be a useful part of more than a few Commander decks in the future.