MArcomage

At this moment this keyword is underused and I'd say slightly underpowered, because of VERY slow token counter (10 + 3N). You need 4 turns with full Mage hand just to get +1 magic (3 with Librarian which is pretty expensive for a common). Mage keyword relies on high magic, high gems and supporting cards very heavily, and it's not hard to disable it completely with early Immolation, Trickster (say bye to your 98 Mage tokens) or Destruction overall.
Defense? Mages have defense, it's called Ice queen, it's amazing, but it's completely unreliable, because it doesn't have Mage keyword. So you need to use Magic portal (5 gems), Wish (6 gems), Scepter of evolution (8 gems) to summon Ice queen, or just play and hope on draw in the right time.
Please, make this counter more reasonable - something like 12+4, or give Mage keyword to Ice queen. Mages really need faster enabling, considering that they use basically only one resource that is the most expensive in game.

Somehow no one seemed to complain until now. Low token count is because of those quick mage cards i think.

I think +4 instead of +3 could not hurt much.

Token bonus is what it is - a bonus, not a goal.

Adding mage to ice queen would be an overkill.

Swift Mage cards are pretty expensive and have very low damage/cost ratio. You need at least 6 Magic to play Swift without fear that you will be out of gems after 2-3 cards played. Legends are useful (Frost unicorn especially), but also pretty expensive.
EDIT: And Mage token is crucial for Mage deck. If common Mages can raise gems (but they are really weak and not so cheap), uncommons are really expensive (except Summon master) and need both gems AND magic.

It's worth noting that the Mage keyword has cards that arbitrarily increase the token count ("Mage tokens +30", "Mage tokens +40") as well as cards that give superior effects if the token threshold is above a certain value. Changing the basics of Mage tokens now would require a lot of tweaking in other places to keep things in balance, and this balancing involves other keywords, too.

I'll acknowledge that it has slow gain by itself, but I've never felt that it was difficult (or necessary if your deck is adequately equipped with +gems and +Magic effects) to activate the effect.