Finally got rank 4 as Mage. Some are quite hard as Mage so I thought i'd do a write up about them.
For reference, my ilevel was 472 but in the end it was 477. Most of my stuff is LFR, crafted or quested. I used a flask w/alchemist bonus and pre-potted as soon as I teleported with the INT potion. I highly recommend Deadly Boss Mods if you don't have it. Really helps.
I also started as Arcane until mid-way in Rank 2. I re-speced fire in anticipation of 5.2.
OKAY here we go.
Rank 1
Bruce
Straight up DPS race, I blinked away during Chomp Chomp Chomp and just burned him down.
Vian The Volatile
I blew all my cooldowns and burned him down pretty fast. One thing to note is that I have Arcane Blast glyphed so it automatically applied Slow, along with Counterspell which let me cast it while casting (sup dawg!). Overall, not TOO difficult for ranged classes I believe.
Goredome
Staying out of the charge was trivial for me, but i'm very very used to being "slippery". Mirror Images helped a lot here, if I had John-Dar's trinket here it would have probably helped immensely too.
Dungeon Master Vishas
It was a game of keep away, glyphed frost nova and talented frostjaw due to the lower cooldown and activation. Note: I totally forgot Deep Freeze even exsisted, so I never used it until rank 4.

Glyph of Slow helped a lot too. And as always, Mirror images helps to soak a lot of damage.
Rank 2
Dippy
Trivial for Arcane; my blast is so fast he never got close. I just paced myself so he wasn't stuck to a wall.
Kirrawk
First guy to give me major trouble. His twisters have a much larger range, and if you're lagging you're screwed. This is the first fight I considered fire but I managed out in the end. Burning all my cooldowns when I was safeish and keeping nether tempest on him at all times.
Fran and Riddoh
I respeced Fire for this fight, mostly for the Alter time combo. in short, it goes like this: Proc heating up after a crit, inferno blast to proc Pyroblast! buff, then blow Presence of Mind and Alter Time. I got a macro for that combo since PoM is off GCD. After it's simply casting instant Pyroblast twice, hitting the Alter Time macro again and Pyroblasting twice more, ending with a glyphed Combustion which has the bonus of stunning him. This does about a million damage over 6-10 seconds and usually wins me matches. The other reason is Scorch; it can be cast while moving.
The fight itself is timing. I did it like this; target Riddoh and fireball until first goblin device
wait until the mines drop THEN blink and then ATPyro combo, using images for mitigation again. Once Riddoh is down, spam Scorch while running around Fran since he constantly tosses stuff at you. Took me a few times.
King Kluaka
DANG HE'S HUGE. He hits like a truck dual weilding two-handed trucks. Like bruce, it's a race but also a game of keep-away. Glyphed frost nova, Frostjaw, Dragon's Breath and Combustion all help here. I glyphed Frostfire bolt here for added slow as well.
Rank 3 *sob*
BLAT.
He splits a lot and his clones move slow. Mark or Focus him asap so you don't lose him, then nuke him down and play keep-away a lot. in retrospect Ring of Frost would have been better here.
Sanoriak
I honestly don't remember much. I think I beat him on my dry run, using images to eat his nukes and ATPyro comboing, along with glyphed counterspell to stop his flame wave, which is what you need to worry about.
MOTHER. BLEEPING. IXX.
He's huge and you have 1.5 seconds to get out of the cone (devastating thrust) or you die. Deadly Boss mods is CRITICAL here, as it'll give you a timer when its cooldown is up. What's cheap is that he's HUGE and his targeting circle on the ground is also a hitbox for his instant kill, so you need to stay really, really, REALLY close to his middle. My basic idea was nuke until first thrust, BLINK ASAP and if I survive, start ATPyro combo. At the 1-2 second mark for Thrust i'd use mirror images to keep him in one direction and run since blink is on cooldown. On the 3rd thrust blink would be ready and after this, if he wasn't dead I would be. It took me 750g in repairs to kill him, and even there I think it was luck with Pyro crits and a large Ignite/Combustion dot. I hate this one. A lot.
Mazhareen
VERY difficult, but fair. UNLIKE THE LAST ONE YES I'M BITTER. Since she hits much stronger the weaker she gets (200k+) it's a legendary game of keep-away. I nuked her but held my cooldowns until about 30-40%, then frost nova'd and blinked away. I did the ATPyro combo at this point too, along with my cooldowns, used images when she got close. Frostjaw'd then Deep Freeze, which I remember existed at this point, blinked away and dragon breath when she got close again, nuking as much as I could all the while. Note: I have /stopcasting macros on all my survival abilities, like Dragon's Breath.
Rank Clock'em
He's cute and damm useful! Great Counter to magic-using dragons.
Hope it was useful to someone, even if you're not mage you probably could get ideas and such from this I hope. @.@
Stupid Ixx.