In wrath, the game came to a point where you were rewarded for stopping people from executing pretty fast, albeit orchestrated and predictable setups. Let me explain-
A fire mage basically exists in two states, either Holy-Shit-OneShotting-Someone, or not. When he's not, he's usually spamming random globals doing anything but real damage or heavy pressure. When he is, pyro's are flying across the screen already and it's too late. The difference between a good player and a great player is catching a mage when he's in the middle of transitioning from running around doing nothing, to holy shit one shot mode. For a fire mage, that transition starts with shielding and ends with casting frostjaw.
After that, it's boom-boom. In the case of the video, neither melee are in cc while both casters congregate around the pally like there's about to be a lynching. This is usually a good indicator that someone is about to get merked, and that you may want to consider aiding this person. A good healer will also usually say, Help me, I'm about to get merked- at this point the microphone will still be on his/her face. Is it a lot of time? No, and is it gimmicky that fire can do this? Yes- not for nothing but fire has always been that way since BC (pom pyro anyone?). That doesn't mean you can't stop it, and the reward- considering how much insaaaane damage fire puts out when a target isn't frozen, is well worth the discipline to stop it.
I'm not going to sit here and list the number of interrupts that could have been used in that ONE anecdotal instance of the video, but I will say this. No, it isn't fair to assume THOSE cooldowns will be up EVERY deep freeze to stop a burst attempt from a good team (where you need to use some cc to gain pressure). But it is fair to assume that a good team would coordinate to have SOME cooldown, even as minor as gouge, to peel a fire mage burst setup.
edit: Stating this just to be clear that I am not in favor of the silly burst fire can dish out, but I do think it's reasonable to expect players to be able to adapt to repeat scenarios