World of Warcraft feels like a real time game but in fact stuff generally happens only once a second. This slow speed of the game has important ramifications for game balance.
One of the amazing things that makes Warcraft fun to play is it feels instantaneous. Even thought the real game is happening on a server 200ms away from you, when you're playing everything feels fast and immediate. If you've been playing networked games for 10+ years you can appreciate what an accomplishment that is. Even modern games don't always get this right, the lag is one of the big reasons I never played much Lord of the Rings Online. (Too bad, it's a beautiful game.)
The primary reason the game feels fast is because your client gives you visual feedback immediately when you press a button. But behind the scenes the game is actually quite slow. Almost every single action you take is limited by the global cooldown, no matter how fast you mash buttons you only get to take one action every 1.0-1.5 seconds. And any damage-over-time or heal-over-time you cast only takes effect every 1-3 seconds. Basically the whole game is marching along at a relatively slow one-event-per-second. That's actually pretty slow for humans: our general preception and reaction time is about 0.3 seconds. But there's enough flashing graphics to keep us distracted from the delays.
Classic World of Warcraft is slower than the expansions. In particular all the old HoT and DoT spells are on frightfully slow timers. The classic druid heal Rejuvenation ticks every three seconds, for instance, an eternity. By contrast the BC druid heal Lifebloom ticks every one second, much faster. Even though the actual average heal throughput (heals per second, heals per mana) is similar for the two, Lifebloom's three times as fast.
These speed differences affect game balance. Lifebloom heals someone faster and sooner and might save their life. In fact the first tick of heal comes in 1.0 seconds after the button is prssed, faster than pretty much any heal in the druid's arsenal other than cooldown abilities like Swiftmend or Nature's Swiftness. Interestingly Blizzard's about to change that with the 4 pc Tier 8 resto bonus, which lets Rejuvenation heal for an extra tick immediately on cast. Which may be too good a bonus, the kind of set bonus that will be too costly to break.
As a melee class feral druids mostly don't notice the slow ticks. All our major abilities are instant cast. Rip ticks every 2 seconds and Rake ticks every 3, but those timers only really matter if you're trying to get an extra 1% dps from perfectly refreshing a bleed without clipping it.
I do occasionally think about the 1 second GCD when I'm trying to hit a fast moving mob that just spawned. It's not a lot of time to tag the mob with a Swipe if it's running away from you. The one second tick timer of Consecrate seems to cause paladins problems occasionally, too, where a mob runs through the aura so fast it never gets hit. Interestingly Death and Decay seems to tick every 0.85 seconds; is that Morbidity, some haste effect, or did Blizzard make this new ability faster?
I wish Blizzard would just re-tune all DoTs and HoTs so they ticked once a second. Or even faster. The recent change to real-time energy, health, and mana generation has worked very well, maybe they can go back and tune up the time effects to make the game feel faster too.