I thought it would be easy to balance all that, once the requirements are clear.
To me, requirements would be:
- fighters of similar levels would need many blows or spells to kill each other (otherwise there's no show to watch)
- magic looses precision and damage with distance.
- The mage still has the advantage of weakening his opponent before (and if) he comes to contact.
- Mages can walk while casting, but not run (not without tripping, or at least serious chances of failing the casting)
- Weapons quickly slice a mage who doesn't use protective spells.
- Magic projectiles are stopped by walls, rocks, or whatever the target is hiding behind.
- Physical armor does protect from ranged spells, one way or another.
- The most damaging spells go straightforward and can be dodged. More subtle magic can actually chase the target.
- Mages definitely are disadvantaged in close-combat. Their point is to keep the enemy at a distance. But that should not be accomplished by running.
- Mages keep their main advantage: zone spells. An arch-mage can incapacitate an army of nobodies, only to worry about some survivors of higher calibre.
- Mages also keep the advantage of a larger arsenal: they can blind, paralyse, cage, mind control, etc.
There is more, of course.
If balancing is achieved now, one side will probably still have an advantage for a while, until everything is in place (ranged weapons, magic items, etc.).
In the end, I think powerful mages should have it easy in open space, and clearly harder a time in a small room.
Btw, a claymore is not a 2-handed weapon. It works fine with a shield. But 2 long weapons only work together in fantasy settings. So there are decisions to be made there.
Also, a dwarf may look odd with a claymore, but all races can currently use the same weapons in the same ways, and wear the same clothes and armor, regardless of their size. So this is not a claymore issue. So far, dwarves wear dwarven boots, so they swing dwarven claymores. Rob Roy / Liam Neeson is not the height reference of yliakum.