Try to understand the battle as a whole
First of all, thanks for a well-thought out question, Veni. I've actually gotten quite a lot of questions about this very subject in the past two weeks, so I'm pleased to see it's an interesting topic for a lot of people.
Most of it has to do with knowing a ton about the big picture. Keeping a big view of the battle has always been one of my strongest characteristics (although I have far more numerous weak ones, mind you). Being able to figure out quickly what the enemy team wants to do is why my teammates usually want me to call out targets (which I don't like doing but begrudgingly end up agreeing to anyway).
I care a lot less about exactly what cooldowns have been popped than I do about what the enemy team's next move is. A lot of people base decisions off what cooldowns are available to both teams, but that's usually an unnecessarily complex and narrow way of viewing an arena battle. So how do I tell what an enemy's next move is? Well, it's pretty simple -- you just look at health bars while keeping an eye on position.
People get very scared (or excited, depending on what side you are on) when health pools drop to 50% or lower, usually foolishly using their powerful, short-term immunities or absorption cooldowns far earlier than they need to. Defensively, I've seen people pop trinkets, Pain Suppression, Divine Shield, and Cloak of Shadows all on one burst attempt. Clearly, this is poor communication, but this kind of thing tells you something very important about most players -- they play in an overly defensive manner and are overly scared of dying.
Likewise, I've seen warriors pop every cooldown they have in order to try to get a kill on an enemy that is sitting at 90-100% health. It's just not good arena play, and they should really be more patient. (I've seen gladiator warriors and even some rank 1 gladiator warriors do this, so it's not like this is uncommon).
What would enemies do?
My "secret," if you can even call it that, is just watching health bars and putting myself in the shoes of the enemy team. I watch a lot of arena videos, and I only occasionally hear people say things like, "They're going to use Pain Suppression now..." or, "The warrior is going to switch to our healer in 5 seconds and attempt to burst him, try to CC the hunter." I find myself saying things like this all the time because to me, it's obvious what opponents want to do when you stop trying to only play your class and play the battle.
Now, in defense of many PvPers who take the time to make very entertaining videos, not everyone attaches Skype or Ventrilo, and I do hear things like that from top-tier players in their videos pretty often.
Instead of trying to eke out a max DPS rotation or get perfect crowd control chains on enemies (which isn't bad practice, don't get me wrong), people should be focusing more on "guessing" what their opponents want to do. It sounds simple, but it's actually quite difficult at first to try to figure out what your opponent is going to do next.
Exploit your weaknesses (not your strengths)
Every rank 1 team I've been on has had discussions at great length about the best way to beat our own team. I'm not talking about a mirror match -- I'm talking about a conversation where we try to theorycraft ways to defeat us. That's right, we actually discuss the specifics of enemy team strategy and composition against us. We attempt to find the best composition that can beat us and what type of strategy they can use against us. That way, when we fight this "countercomp," we already know what they're going to do.
I'm sure tons of teams at the top do the same thing -- I see some pretty ridiculous win percentages out there (95%+). The best way to win 19 out of 20 games (or more) is to know how your enemies are going to try to attack you and stop them before they get a chance. Likewise, knowing what your opponents are going to do before they do it is instrumental to a successful strategy.
Imagine you sit down at a chess game and you know what your opponent's next move will be after you make yours. You will have a ridiculously huge advantage that will almost assuredly win you nearly every single game of chess. I've heard that grand masters play on this kind of a level, but five to six moves in advance.
In arena, I've played on teams where we know what our enemy's first target will be, the signs to look for that they're going to switch, their switch target, and even a tertiary target. We'll nullify all of their attempts while mixing it up each time against them so they don't think we ever use the same strategy. This also has the beneficial side effect of exploring new ways to deal with certain compositions.
Variety is the spice of life -- a proven way to stay successful
One of the biggest mistakes a high-level team can make when fighting other high-level teams is to use the same strategy over and over, even if that strategy is proven to work 99 times out of 100. Perhaps there is a better way to attack them that you haven't discovered, and you're sacrificing it for some arena points. It's a short-term victory but long-term failure.
Keeping the enemy team on their toes is what you want, anyway. Even if you're using a subpar strategy, it will most likely be one that they didn't expect, which can lead to some hilarious stories. Back in Season 4 of The Burning Crusade, the 5v5 comp to beat was euro comp (resto druid, discipline priest, frost mage, warlock, rogue). Most teams sat on the warlock or rogue the entire time and didn't attempt to kill either the healers or the frost mage, as they were much more survivable.
When our team found ourselves going up against the #2 team on the battlegroup, which happened to be a euro comp, we bounced between the frost mage, priest, and druid. This was the exact opposite of the common strategy used to defeat euro comp. The other team was understandably stunned.
The warlock and rogue were never in a position to free cast or DPS, so they made tons of mistakes they otherwise wouldn't have. Likewise, the mage was rarely under pressure from other teams, so he used defensive cooldowns very poorly due to a lack of experience. The druid stopped Cycloning entirely, which allowed our DPS to go crazy, and the games were not even remotely close. The "best strategy" against teams is not always the best strategy to use, if that makes sense.
What this means to you, the frost mage
Okay, so I spoke a lot about team interactions here and gave a whole lot of nothing about when to use Frost Nova or Ice Lance. When you understand what the opposing team is going to do before they do it, you'll easily figure out what you have to do in order to stop them from advancing their game plan.
Does that warrior have tunnel vision for you? Root him in place and Blink around a pillar while spamming instant-cast spells to keep damage high on your primary target. Tell your team that the warrior is tunnel-visioning you so they can compensate for your additional movement (and lack of burst capacity). By working together to neuter the warrior, you can execute your game plan much easier (whatever it may be; remember to change it up).
That's only one example. Hopefully by discussing a broader range of subjects, I've helped out more readers along the way. Let me know in the comments below!
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