Hey
Regarding the questions lately about pyro..
POM/Pyro takes skill! Despite what your victims say. You need to consider your opponent's class and abilities when using it.
Firstly, you need to make macros to use it effectively.
Typically a pom pyro involves a number of steps:
1. Arcane Power (+30% damage)
2. Trinket that gives + damage for a short time, like Vengeance of the Illidari
3. Presence of mind
4. Pyroblast
However, you may be in a situation where you want arcane power without the instant pyro (e.g. when opponent is sheeped). Therefore I use 2 macros. One for steps 1 and 2, and one for 3 and 4.
http://www.worldofwarcraft.com/info/basics/macros.html for basic help on this, use /cast for spells and /use for trinkets.
Consider Trinkets
Every class has a different trinket, and some of them remove polymorph. Shamans, Hunters, Warlocks and Druids cannot remove poly with their trinket. However druids are immune, hunters and warlocks have pets, and shamans have earthshock and grounding totem. These are hard people to sheep but it can be done. (Warlock trinket was only recently changed so they'll HATE you for sheeping them ;)
Here's a tip for sheeping shamans - their earthshock range is 20 yards but poly is 30. Use frost nova then blink (20 yards) away, then sheep them twice. If the shammy is good they'll use grounding totem on the first one which is immune. However your second will hit the shammy as the totem is on cooldown.
Using sheep
If you manage to sheep someone, don't be tempted to use poly just because you have it. There are smarter options. Like ktangent said in a previous post - getting two large crits back to back wastes the ignite on one of them. If the class I'm fighting has melee, I often use arcane power/trinket macro, then highest frostbolt, then pyroblast and fireblast. There's now 30 yards they have to make up, while slowed, after eating about half of their health in damage. EAT IT UP!
However having said that, twin pyros look incredibly cool and will have them pissing themselves. Just realise it's not the only option.
Rogues
They have cloak of shadows. This makes them 90% resistant to all spells for 5 seconds. This is where you can really trick them - if you use 2 macros like I suggest.
When the time is right, fire your arcane power and trinket. The rogue will recognise this and think it's time for you to launch pom pyro. Don't do it. Just run away. After about 4-5 seconds, let loose a barrage of your instants.. pom/pyro, fireblast, blast wave, frost nova, icelance etc. The rogue will have wasted the cloak of shadows, and all of those spells will still be +30% damage.
Warlocks
I'm 67 at the moment and today I killed a 69 lock in world pvp 5 times, and died only once. I also killed a BM hunter in square even combat, which are usually magekillers. The trick with these traditional mage-eaters is fast damage and lots of pressure.
Usually their pets are too annoying to allow you a polymorph. I open with guns blazing - arcane power/trinket/pom/pyro. Follow up with a fireblast while running towards the lock, then blast wave to hurt the lock and slow the pet. At this point, a pre-emptive counterspell is great - the lock won't know what the hell to do and they'll have about 1/3 health at this point, all in about 6 seconds.
From here it's just instant cast spam. Frost nova and icelance is a good option, then AE and fireblast.
Also if you have insignia of the horde or are undead or both, have them bound and ready when you face locks. Breaking their fear as soon as it lands makes them upset, and dead.