is an odd card. As mentioned, it has more impact the more competitive the meta is. Turns off when untapped, similar to Winter Orb
and Howling Mine
, which opens up some potential for asymmetry. Obviously most oppressive as part of a dedicated mana denial plan. I don't think that it goes in most decks though - it can certainly slow some decks down, but most curves are high enough to not be affected too badly. Simultaneously, there isn't enough consistency to play it turn 1 or 2, like you would want to do in Legacy/Vintage, and making your own curve entirely 3+ mana spells to take advantage of it isn't a very good strategy either.
I've hypothesized about making an Orb/Sphere tribal deck before, but it ended up just being a stax/prison deck - Trinisphere, Winter Orb, Static Orb
, Sphere of Resistance
.... Also Story Circle
and friends, if you expand it to other round cards.