Oakflesh/Stoneflesh/Ironflesh/Ebonyflesh/Dragonhide - Alteration spells that temporarily boost armor rating up, and Dragonhide making you take 80% less damage for like 30 seconds, though it is a 2H spell.
As others have said, can be using a one handed or two handed weapon. Restoration magic is your friend. I don't use wards as often as I possibly should, though when your HP is running low, a good heal spell is helpful. My currently level 172 Breton started out pretty battle mage-ish (as Bretons often can be) I started out using a sword and healing, switching that out to flames. I leveled illusion excessively and got myself far behind in levels to my enemy. I then focused on using the above mentioned alteration spells to survive better. Once I had Dragonhide, I could survive well for short times, though used Lydia as a meat shield. Then I focused on Conjuration, as head on fights weren't going well, and I retired Lydia to get more XP myself. I got had all 3 of those to 100, got 100 enchant and my spells became free cost in 2 schools. I finished up with Destruction and then restoration. I turned my focus away from being as much mage devoted. Though still often will quick switch to Grand Healing to heal up (I playing on Legendary now) and otherwise use primarily a sword and shield.
Kinda went overboard on this, but the moral is that Battlemages can work, you just got to figure out what works well for you.