An average mage type is obviously going to have a significantly lower DB available, compared to a fighter. They can't wear armor or carry a shield. So, how does a mage avoid getting creamed by the first opponent to get close?
First thing my mages always tried is not having the opponent get into melee range. Spells like e.g. Leaping are your friend when trying this. And the Shield spell can overcome the restriction concerning shields.
The obvious answer would seem to be "spells", but all the defensive spells I'm seeing are single turn, instant spells (i.e. Bladeturn). Since mages are limited to one spell a turn, that would seem to mean that the mage doesn't get to cast anything offensive if he's being attacked.
Having a little bit of OB with one melee weapon is a good idea if there is a high probability that the mage will face a melee encounter sooner or later. Of course, trying to develop ranks with a weapon is quite expensive for a mage, but I prefer it to losing my characters
. A little OB offers the chance to do a full parry for some rounds and survice until the fighters can help. Spells like Blur or Shield are also useful when defending like this and last longer than one round, like Bladeturn does.
For quick mages who can cast Firebolt or a similar deadly bolt there is also another option: Fire the bolt when the opponent gets into the 10' Point Blank range, where the bolt gets +35 to the attack, and hope that the opponent gets hurt so badly that he can't attack. As long as he is kept stunned the mage can keep firing his bolts. This is of course quite risky ... but if the mage can't flee or defend himself using a weapon this might be an option.
Finally: Welcome to the forums!