A full guide on how to measure and tune the power of your Commander deck merits its own article, and I plan to write that soon
Its usually better in the 99 than as a Gruul commander, but it can also threaten lethal swings once youve grown out you land base
If any cards have the keywords Activate: Main or Once per Turn, you can activate the abilities during your Main Phase
(I'm not sure about the correct wording of the ability effect for instance...)
Although Card not found costs four and is thus not very efficient at ramping, it does have a significant advantage in Commander and has seen some play in Modern, where you can find a shock dual with it
However, for a more thematic or casual play, Michiko's Reign of Truth could still see some play for its unique flavor and potential synergy with the right deck strategy