I have been playing it exclusively since I started playing Hearthstone, and though I agree it is a class that can do well, it can't touch at least half the decks out there. Pretty much druids and warriors are auto losses (unless warrior isn't control, which never seems to be the case), any smart paladin/priest that knows when they need to heal themselves can handle us just fine, zoo/hand locks do just fine unless we draw into all our board clears/freezes early (just a matter of rng), miracle rogue wrecks us unless we get a block up before the one shot, shaman is almost 50/50, with freeze mage probably pulling ahead slightly in that matchup. Hunters can take us easy just by running flare(s). Not sure if I am missing anyone.
Can the class be annoying to deal with? Absolutely. Is it overpowered, not by a long shot. Are all these posts/comments regarding freeze mage being overpowered all because some guy did well with it in a tournament setting or do people legitimately feel they are overpowered? I didn't watch it, but I am sure that it only performed well because of rng. All of the players competing in such a tournament have decks that can beat anyone/anything, and they are all very good decision makers regarding plays/what to expect, but ultimately rng (in many cases) is going to be the deciding factor as to who wins/loses. Any class deck could win a Hearthstone tournament given that rng was in their favor.
No particular class is really overpowered anymore than another. Some just have easier paths to success than others. Please get over yourselves and stop only making "This needs nerf/buff, QQ" threads. Play the game, accept that you aren't going to win all the games you'd like for one reason or another, and just have fun. Thanks.