I feel like any class I play necessitates certain NPC party member choices... except for the wizard.
If I play a cleric, it makes no sense to bring Shadowheart along. If I play I fighter, I'm either leaving out Lae'zel or Gale. If I play a rogue I'm definitely leaving out Astareon. If I play a warlock, Wyll is redundant, though I can do without Gale if I want to keep Wyll. If I play a ranger, Astareon becomes redundant again, or Wyll does.
But depending on how I build my wizard, I can replace any other character's role. A shield dwarf or githyanki wizard can double as a fighter and actually performs the role better than an eldritch knight. A halfling or elf wizard makes a passable rogue. Any wizard can learn cleric spells and double as a cleric. With a feat, a wizard can, at level 3, pick up the most iconic warlock abilities.
I don't think this versatility is a problem, but it would be nice if it were a feature of the other classes as well.
Part of this comes from the availability of the warped headband of intellect early in the game. Once again, not really a problem, but it is a bit unbalanced. A way to solve this would be to include (warped) gauntlets of ogre power early in the game as well. These would set the wearer's Strength to 18. These two items might even react violently to one another when equipped by the same character (maybe causing bane until one or the other is removed). Another option would be gloves of dexterity, or better yet, an item to enhance the traditional D&D dump stat: Charisma. Or maybe replace the warped headband of intellect with an item that changes a different ability score depending on what slot it's equipped in (head: INT, arms: STR, hands: DEX, etc.).
Either way, as it stands, the wizard is clearly the most versatile class. It would be nice to spread that around a bit, and not just by giving every class wizard spells.