Couldn't tell you specifically on the actual numbers. I can explain the "why" though. Hit doesn't need to be much higher because you're taregting lvl 85 "mobs". I think you're kinda looking at this the wrong way though. Proceed with this step by step. Going off of what you mentioned from Arena Junkies.....
1) Get hit to 4%. Should be REALLY easy. You likely already have this.
2) Get Spell Penetration to 240. Either the neck piece or cloak from honor gear will land you this.
3) As for INT, I'd be gemming straight up for that, and manipulating the other stats with reforge. +40 INT gems in every slot except the ones where you get a +10 or more INT bonus from an arrangement. Thing is..... gemming is one of the FEW places you can gain more INT, so don't waste it on secondary stats.
4) Push for 25% crit with reforges.
Looking at what you have, you're just about there with hit. You're kind of a bit all over with your reforging. I see crit to mastery. Crit to haste. Haste to crit. Mastery to crit. It's not the end of the world.... you just need to progress logically and orderly. From where you are, right now?.... Here's what I'd do....
Go back over my reforged items. Going one at a time.... reforge back anything that I reforged crit off, and switch it back to crit. Stop. Check my paperdoll. Did I drop below 4% hit? No. Did I lose intellect? No. Did I lose spell penetration? No. Am I at 25% crit? No.....
Then progress to the next piece.
The only thing about what you have that I question is the choice of trinket. Personal view, but for PvP, where you want burst damage on demand as much as possible, I'd go for the on-demand spellpower increase trink. Hold that in reserve for the close fights where you have an opponent down, and need to finish them off quickly.
I don't think there is an easy answer to this. You're just going to have to make a tactical choice. Example: on my pally, I switch frequently between auras. My default though is resist. Why? Because it's one of the few sources of magic resistance available. Against a well-geared mage/lock.... it won't make a huge difference, but it can help. If I see a melee heavy group, I might switch to devotion.
Main thing is..... you have to make some tough choices now and then.
Personally, I'd never drop the cc breaker. You already know my thoughts on the spellpower trink. Burst damage on demand trumps. Especially if you're dealing with a healer. That can be the difference between a win and a loss. Finishing off an opponent like a holy pally before they can tick a big fat heal, or worse.... bubble.... is important. And don't kid yourself.... you will NEVER be able to out damage what they can crit on a heal. Even my crappy holy pally lands 70k+ crit heals. And as a healer... I don't have to contend with resilience. You as a damage dealer, DO. And mortal strike is a joke compared to a fat 45% to 50% damage reduction from resilience. I still have a 25% advantage over you as the damage dealer.
At the end of the day, keep multiple trinks ready for various scenarios. If you're running arena.... you'll likely want a different set up. Who you're running with will also largely determine what you want to do. Trinks are essentially your customization-per-fight tool.
Anyway, hope this helps you figure out where you want to take the mage.