Mulligans
General Mulligans
This deck only has the one 1-drop so obviously you're keeping Secretkeeper every time. I'd also recommend keeping Eaglehorn Bow and Cloaked Huntress (especially on the coin), and Doomsayer against Aggro and Tempo. Nothing else is an always keep. Keep secrets judging by the matchup. Pretty obvious, Explosive Trap good against aggro, Snipe good against Tempo, Cat Trick good against control, etc...
I found this deck on Reddit (https://www.reddit.com/r/CompetitiveHS/comments/734whb/doomsayerputricide_secret_hunter/) by Ryan Pres. I made a few little adjustments to his list but basically its pretty solid. Control Hunter is kinda the white whale of the Hearthstone world but this is an original approach that I think might work.
Most secret hunter decks only run the one or two strongest secrets, so they’re easy to play around. But this one runs 10 (12 in his version, but I dumped the Snake Traps for Secretkeepers). Stitched Tracker and Tracking prevent your hand from being loaded up with too many secrets and give you decent draw. Basically you own the early game with a barrage of unpredictable secrets and then you have very powerful late game cards (Bonemare, Highmane, Rexxar Beasts) to help at the end.
I have only played it a little bit before work but I went 7-0 to rank 15 (not the best players, but it’s early in the season and there were tons of good decks). The best part is that its especially good against Priest, this deck really seems to rip Razakus to pieces. I may make some more adjustments after I get to playtest it more tonight. I’m not sold on the Tar Creepers and the lack of direct removal like Deadly Shot and Kill Command could be an issue but so far the secrets have just completely baffled my opponents. Two of the three Priests I played quit at above 15 health after playing directly into secrets several times in a row.