Hearthpwn

You HAVE to control turns 1-5 (1-4 if he has The Coin, and doesn't use it to turn 2 Muster for Battle).

If you can turn 1 Twilight Whelp into turn 2 Wyrmrest Agent with a dragon in hand, you're off to a running start, since most of his early minions are going to be 1/1 and 2/2.  Getting a 4 health Taunt out there is huge, since the only way he can deal with it prior to turn 4 is to swing into it (while you still have a swinging 2/3 that can help take care of the Divine Shields and Hero Power minions).

Your absolute best cards against a Secret Paladin as a Dragon Priest are Holy Nova and Lightbomb to keep his board clear.  Holy Nova will deal with most of his minions (especially early), and Lightbomb will deal with ALL of his minions (that aren't protected by Divine Shield).

If you find that you can't get answers for his turn 5-6 Mysterious Challenger and don't have the 2-turn combo mentioned above, you can almost always find value in a turn 1 Northshire Cleric.  You should be able to trade well early and use your Hero Power to heal it for the extra card draw to get an answer.

Coming from someone that plays a Secret Paladin, Dragon Priest is one of the hardest matchups I've found so far, especially with my personal version of the Secret Paladin leaning more toward the early game, more aggro-y version (still haven't crafted/drawn Tirion Fordring or Dr. Boom to gear more toward the Midrange version).

If you're looking for something to buff your tokens, then Warhorse Trainer should be your go-to choice.  The downside to Warhorse Trainer vs Quartermaster is that the buff is lost if the Trainer dies, and he will become an immediate target for your opponent. The positive, however, is that if you can keep the Trainer alive, he will buff any tokens that come in after him, whereas Quartermaster is a Battlecry ability.

You want to have the Mysterious Challenger to play on turn 6 (turn 5 if you have The Coin). It's one of the single biggest tempo swings available at the 6 spot, provided you aren't holding one of the secrets he could play. At the worst, you play him on your empty board and their next attack is foiled, then he's buffed to 9/8, then your Defender comes back as a 2/1. If they don't deal with both minions, Competitive Spirit procs. Now you have a 10/9 and a 3/2. For 6 mana. On turn 7 (6 if Coined).

This play pretty much swings the match unless you are just REALLY far behind or if they manage to Fireball/Hex/Polymorph/etc the Challenger before your secrets proc (at which point they still have to devote resources to killing the defender the 2nd time or you still end up with a 3/2, and if they don't deal with the sheep/frog, you now have a 4/3 or 3/3 Taunt respectively).

Mysterious Challenger is the crux of a Secret Paladin. If you get it in your opening hand, you RARELY want to mulligan it.

That being said. If you're on the play and you get something like Mysterious Challenger, Consecrate, True silver Champion? Then you probably want to mulligan it for lowe drops. But if you get Mysterious Challenger and a one and two drop or a one drop and Muster? You could keep it there, as you are guaranteed to drop 3-5 bodies on the field the first 3 turns.

I ALWAYS keep Mysterious Challenger when I'm on the draw. He's a monster at turn 6, but at turn 5? Good luck to your opponent.

NOTE: The title of this deck is a little deceptive. This deck is more midrange with a few aspects of a Secret Paladin, as opposed to a true Secret Paladin. Therefore, for this specific deck, it may be better to mulligan Mysterious Challenger.

It could be worse.

You could draw and play Troggzor the Earthinator turn 5 in Too Many Portals! Tavern Brawl and go on to lose the game.

Just ask my opponent that I just faced :D (Polymorph ftw!)

5 games isn't nearly enough to determine whether a deck is good or bad. At 5 games, you still don't have a feel for how the deck should play out, not to mention that it's very possible you simply caught 5 bad matchups for this specific deck. Every deck has counters and matchups that are more difficult than others. That doesn't make the deck bad. There are just some decks that it will struggle against, and normally at least 1 deck that counters it completely (like how I cry when I'm playing my Freeze Mage and catch a Control Warrior, which is basically a loss at turn 1).

That being said. Every deck also has decks it's favorable or even almost insta-win against. If you like this style of play, stick with it. Make adjustments as needed. Eventually, you'll learn the deck and know how to give yourself a better chance even against an unfavorable matchup.

OP has clearly stated in the guide an anti-aggro hybrid variation of this deck.

Additionally, you should take it upon yourself to modify the deck to make it better against the matchups  you're seeing. No deck is ever an end-all-be-all-100%-win-rate-guaranteed-to-reach-Legendary list. It's a list that SHOULD give you a good win% with some modifications for whatever you're facing in Ladder.

If you're seeing a lot of aggro and Paladins, switch Freezing Trap with Explosive Trap and drop Stranglethorn Tiger for another Glaivezooka to help clear their early board. If you're facing a lot of Secret Paladins, swap out Hunter's Mark or Loatheb or Strangelthorn Tiger for a Flare, as well as taking out Freezing Trap for Explosive Trap for board clear.

Take it upon yourself to make changes before you post that a deck isn't good because you're facing a lot of bad matchups for that deck in Ladder.

The "rule" from Magic applies to Hearthstone as well:

If you lose and the opponent has 1 life, you probably misplayed at some point.

That being said. The effectiveness of this deck really relies on BOTH players' draws (beginning and subsequent turns) as well as your opponent's ability to recognize what they're up against. If your opponent can't board, doesn't get a Taunt, and doesn't realize that keeping your board clear is vital, you win. Subsequently, if your opponent draws a Taunt and you don't have Sap to deal with it, or if you can't draw the minions to keep the pressure up and you lose tempo, you're dead in the water.

The efficiency of Annoy-O-Tron can't be overstated in this particular deck. Not only does it provide Taunt to protect your minions, but it also sets up potential dagger kills, which further protects your minions by clearing the board. It also plays as a nice counter to Muster against Paladins slows down a lot of heroes that might use their hero power to help kill it (Mage), and deals at least 1 face damage to weapon classes, which helps accelerate the deck slightly, as every damage counts when you're rushing the opponent down.

While Conceal does protect your minions against the opposing board and hero power, it offers you 0 protection if your board gets wiped (Annoy-O-Troy can still force the opponent to deal with it and buy some time). Shadowstep is pretty much always a dead card, unless you're using it on Annoy-O-Tron, which DOES set up nice combos and offer more minion protection, but also slows you down and let's your opponent get 1 turn later into the game and the chance to draw an answer he may not have otherwise gotten.

Edit: having forgotten the power of Shadowstep + Charge, Shadowstep could definitely find use. The problem still remains that Shadowstep is pretty much dead until the turn you go for lethal, or if you attack with Annoy-O-Tron that's lost its shield and Shadowstep it back and replay it that turn so it's still able to attack next turn.

As I stated, he definitely has uses, but his uses are more limited in a deck that's trying to rush the opponent down simply because he doesn't have Charge.

The main spot I can really think of where he is most efficient is if your opponent has board control with Taunt mobs down, you're holding Blade Flurry, and you're 1 damage from achieving lethal. Then you can drop him and Blade Flurry for lethal.

Again. I haven't tried it, so I can't truly say. But just in theorizing the deck in most matches and comparing him 1:1 with the other monsters in the deck, he just seems clunky to me. That being said? If he works for you, awesome! :)

I was wondering this as well. Not only is it a 3/2 body that can be used to help deal with Taunt, but it also increases your dagger effectiveness at clearing the enemy board or can help set up lethal with Blade Flurry.

That being said. I've played this deck in 5 games to a 4-1 record now, and while I haven't tested it, Auto-Barber just seems too slow and clunky for what this deck is trying to accomplish. In all likelihood, you wouldn't drop him until turn 3, which means you're missing out on dropping Wolfrider or Arcane Golem, which means you're trading 3-4 potential face damage on turn 3 for 1 extra weapon damage.

If you drop Barber turn 3, the most damage you can get from him + battlecry by turn 4 is 7 (3 from barber, 4 from 2 dagger), but that's assuming you didn't attack on turn 2 when you made the dagger and attack with dagger on 3 and 4. Meanwhile, the minimum damage you would do by turn 4 from a Wolfrider is 7 (2 attacks + 1 dagger), or you could do a minimum of 9 with Arcane Golem.

Additionally. You already have Buccaneer in the deck, and dropping it turn 1 forces your opponent at worst into a bad trade, and at best into taking 4 minimum face damage turn 2. If you're on the draw and have The Coin? It's a minimum 6 damage turn 2 if you can Coin into two 1 drops turn 1.

TL;DR

While there are certain situation where it might have a niche, ultimately, Goblin Auto-Barber is just too slow (in my opinion)