It is a deck, that is the least fun and interactive to play against.
Secrets block you out of doing anything without getting punished almost everytime.
Basically you need board presence, removal and a ton of healing to beat it - all things secret mage can counter with its secrets (Explosive rune/counterspell/duplicate). Not to mention that it can cycle through its deck pretty easily.
For me these encounters are frustrating and I encounter mage 80% of the time on ladder.
I'm having success against them using Reno Mage ft. Quest and modest Dragon package. I'm rank 2 now. Took me a while to figure out what list works well for me. Now I do well vs. aggro due to absurd powerlevel of individual cards, deck is so stocked with powercards that I see good cards every game. Quest allows me to cheese out wins vs. decks that would otherwise outvalue me.