[Radek]

Mage/FIGHTER? It sounds like a nonsense. Why is the mage part here? To allow the mage/FIGHTER to cast a few low level spells? Also, let us note that the low level of the mage part grants inefficient casting and that the mage/FIGTER can cast only without (most of) armor.
On the other hand, fighter/MAGE makes sense. It is a mage with essentially improved ability to fight. Even if you will dual immediately at level 7 (not a good idea), your mage will be able to use any weapon and he will be able to place more '+' in the selected weapon skill. A fighter/MAGE need not contribute to final success of a fight only by casting. He can fight as well. This affects the selection of his spells - he will memorize only those spells that are useful against difficult enemies. Easy enemies will be serviced by a weapon.
Mage/FIGHTER is nonsense. On the other hand, thief/FIGHTER isn't nonsense. The low level thief part can be improved by Potions of Master Thievery. A thief/FIGHTER can be specialized in detecting and disarming traps. In the other words, a thief/FIGHER is a figher able of detecting and disarming traps and also of stealing if it is advantageous.