You can give 2 weapons to your pet at level 1 I'm fairly sure, but he won't use the offhand wep.
I think Sam is in the right ballpark, my necro pet I'm sure was dual wielding usefully at 24. You need to be careful of the 50% dps rule if solo though, don't want to give Jebober the tools to out damage you
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Also for necro pets, you can STOP giving them 2 weapons at 44, they naturally dual wield from then on
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What level is your mage? My bet is on 24 for the skill, but post if you're finding they dual wield earlier.