What they meant (I hope) is that if u haven't keybound your abilities, you may not yet know how to counter mages. Or ateast not use abilities as quick as you should. It's a reasonable assumption since keybinding is such a basic rule for PvP. I have seen only a few players who can click abilities as quick as a regular keybind-user in actual pvp situations.
Now, about the damage. Living Bomb seems to be hitting as in retail, like someone else mentioned here. With my frost mage, 522 ilvl, my icelances hit between 80k-90k crits (always crits cos shatter ofcourse). That one 110k ice lance the mage did in your SS, I do not know if he got lucky or used bug but rest of his lances don't hit this hard. Truth be told, there are many classes hitting harder and faster in Warmane's MoP. 80k hits are even laughable at times compared to some outrageous numbers of other classes. I won't say which classes to avoid further rage/whining. Besides, anybody playing a frost mage would know that outside of burst, their sustained dps is not great. So these icelances hit only that hard while in burst.
All of this, plus the fact that all mage specs' bursts are easy to predict, avoid/mitigate if u know what to look for.
Save your trinket for if you need to use while he has orb proccs. Dont trinket his first deep freeze if he's faking his burst. CC/LoS/Major defensives during his orb+alter. Alter time can be purged and if u do, there goes half his burst. This is basic for a 1v1 situation like in your SS (I assume). In arena, your partner can CC as well. Also, before anybody says "mage defending mage" I play all classes except warrior and priest. :P