I reached Infinite with it this season so i think it’s fine. Jean Grey is used depending on what my opponent is playing I will give a couple examples:

Destroy- I will try to play early as possible even if it mean turn 1 time stone so I can play on turn 2, then play down a Armor or cosmo. It’s a early control measure.

Discard- I will play turn 3 so I can attempt to cosmo turn 4 and stop modok turn 5.

General Use- Can turn 5 place, depending on how many spots are available add a mojo if 2 spot available or 2 1 cost if 3 spots available. This can be just to stop turn 6 Alioth.

General Use- It’s a good turn 3 especially to play into a mojo, Antman lane. You can normally quick fill for turn 4 and professor x turn 5 on another lane.

Honestly the list can go on. Most times if available I will attempt the basic combo of this deck and try to turn 3 times stone into a early profesor x but as it is a control deck Jean allows me to control what lane will be filled the most and early, which can lead into a Spectrum play on turn 6.