My group (level 5, including a druid and ranger) just found a magic staff. It has a "twin" complementary staff as well. The one they found was made by a druid who became a wizard, the other one is made by a wizard who became a druid. They taught each other and made the staffs and paired them.

They are supposed to give the staff to a mage patron, but they might not do that now.

My current rules for the staff are:
Staff, weapon, very rare (requires attunement by a druid, sorcerer, warlock, or wizard)
Spells. The staff has 10 charges. It regains 1d6+4 charges daily at dawn. If you expend the last charge, roll 1d20. On a 1, the staff crumbles into cinders and is destroyed.
A druid (primal spellcaster?) can use the staff to cast a wizard spell from the list below by (1) expending an druid spell slot of the same level as the spell to be cast, and (2) expending a number of charges equal to the level of the spell to be cast. It uses the druid's spell save DC.
>Magic Missile
>Knock
>Fireball
>Dimension Door
>Telekinesis
>Chain Lightning
>Prismatic Spray
>Maze
>Time Stop

The wizard version would work the same, in reverse, letting the wizard use charges / his own spell slots to cast from a limited list of "iconic" druid spells.
When combined, both powers would be in play, plus also some synergy power.

My question: is this as insanely broken as it feels to me, to the point of making the druid player even more OP? In a way that will actually damage the game? And if so, how do I tone down this staff without completely castrating it to the point that it makes no sense why their mage patron would want it so badly?