Shield only lasts a few minutes, so you have to cast it at the start of combat. Also, with the revision coming in in a few weeks, that also counts for buff spells (Bull's Strength, Cat's Grace, etc) with Shield taken down to +4. Ranger hit points will drop to d8.
If you want fight and magic, be a Bard. Their spells are a little more deversatile than that of the Wizard and Sorceror, though they get less of them, but they can cast spells while wearing chain armor, which gives +4 armor. They're also better in attacking than mages are, though not as good as rangers. If you consider that you only get the ranger's HP and To Hit half the time and the wizard's the other half, then it might actually balance out.