I think he has a few points of that resistance now. But either way, because the capstone from Astrology scales quite well (being a nuke and all), few points of resistance is of no great importance. Also, welcome to the forums, Isasaur.
Honestly, I've been rocking Tinkering on most of my mages Recently and it's pretty awesome. You can fallback on the crossbow bolts if you have mana problems... My only issue is that I also tend to run Alchemy so I feel obligated to rock rogue scientist XD But really, Tinkering is the single BEST source of trapsight in the game...I don't see a reason not to pick it.
HOW DARE YOU CALL US FRIENDLY YOU MAGGOT I'LL HAVE YOU KNOW WE'RE THE TOUGHEST COMMUNITY THIS SIDE OF BIKINI BOTTOM.