Hey guys, glad you're getting a taste of the grind. Don't have a ton of time, and I've mentioned this a few times in other threads but I'll touch on a couple things really quick.

LOS teams: To be honest, the best way to deal with these guys is be PATIENT PATIENT PATIENT. Just wait them out, if they want to wait til you've wasted cooldowns to charge... then don't waste cooldowns. Keep up groundings and /dance
Couple big mistakes I used to make often:
1: Blowing heroism and they run right back. If they are still mounted, don't use it. Wait til they are on your ass, and dismounted... else a good team will just run away again.
2: Blowing my EM cooldown on someone 5 feet from a pillar, then they just run behind it. This is a more impulsive mistake than anything... as I never actually thought it was a good idea, just kinda... happened lol.
3: Chain casting on people but never actually killing them. Flameshocks, CLs, etc on people. DON'T BLOW ALL YOUR MANA. You'd be surprised how fast I've found myself at 20% mana with nobody dead because of LOSers. Once I'm low mana, BOOM they charge and Im a goner. I focus on recasting grounding totems, watch for pets stomping my tremors (kill lone pets everytime you can), and let my priest get some juicy mass dispells off on people out of LOS (cast to the side of the pillar etc). Naked targets > buffed targets... plus it usually makes them panic and make a mistake.
4. Spellpower: It comes with gear, and so does success, however I also gem/enchant for it as a primary stat... which is something you CAN do now before the gear upgrades come. In a competitive battlegroup, 1900 spellpower will not carry you much past 1500 rating. With totems down, ALL 4 of my guys are sitting on 2700+ spellpower, probably about 2470-2500 without. You will have a hard time killing anyone in Deadly/Furious gear without high spellpower... unless they stand out in the open for 5 seconds... which would put them in the "Shitty Player" column... and you won't see this behavior at higher ratings. (But it sure is fun when you get one of these teams lol. 7 second match anyone?)

Hope this helps. There are some good threads Dominion, Kruschpak, Sinaa and myself have thrown together that covers gearing, gemming/enchanting, macros, totemsets, etc. However there still needs to be a good strategy thread/video, which I am working on throwing together here soon.

Good luck and happy hunting.