This card would be much better if the description of it was “deal one damage to a random minion”. Then you could play it as a tech card against aggressive decks with a bunch of one health minions. A sure kill on Leper Gnome or Worgen Infiltrator on turn 2, Flame Juggle could see play in fast meta. However, because 50-50 chance I do not see it in constructed. If you want something to clear 1 health minions, Mad Bomber does a better job than Flame Juggler. He has ~70% chance of killing X/1 that is alone on the board. In arena, this card will be a good 2 drop that can be viewed as an upgraded River Crocolisk.
This little dude gives +1/+1 to friendly mechs. Obviously you want to play him in mech themed decks, like Mech Mage deck. Mech decks tend to be aggressive. Since minions usually go face, Clockwork Knight’s Battlecry effect can be viewed as “for every friendly mech deal 1 damage to opponent hero”. I would not play more than one copy of it. The only question is what will you cut to make a room for it? In standard Mech Mage deck, you can cut Loatheb if you think Clockwork Knight has a better effect, or one of Azure drakes if you do not value card draw that much. In arena Clockwork Knight is a solid 5 mana cost minion. Mech synergy is not something you can count on in arena, but if you already have few mechs, this card could be a nice addition to the deck.
Take Argent Commander, cut it in half and you will get this card. In every deck that runs them, charge minions are not used as a removal, but as face damage. Argent Horserider paid for its survivability, which comes from Divine Shield, with lower attack value. Argent Horserider could replace Wolfrider in aggressive decks that have ways to permanently buff their minions. In Face Hunter deck, I think 3 damage right away is better than the possibility of 4 damage over two turns.
Eydis Darkbane and Fjola Lightbane
These sisters have powerful effects and 3/4 bodies, which is as good as you can get for 3 mana. Dark sister deals 3 damage to a random enemy when you target it with spell and Light sister gains Divine Shield in same situation. These will be a nice addition to Paladin decks that run Blessing of Kings and Blessing of Might. If the effects prove useful, we can see one copy of Blessing of Wisdom for card draw and extra effect procs. Eydis and Fjola are also good in Priest decks, because of Velen’s Chosen and Power Word Shield. However, Priest already has other minions contesting the 3 mana slot, like Dark Cultist, Injured Blademaster and Deathlord. Will sisters be better than them? Remains to be seen.
In arena, these sisters are Spider Tanks with good effect if you are lucky enough to draft buffs.
Silent Knight and Argent Watchman
Silent Knight is the only minion in the game that has both Divine Shield AND Stealth. It looks really bad in comparison to cards we already have. Shielded Minibot costs less for similar value. Shado of Naxxramus is much better, because it grows over time. Scarlet Crusader trades better with its 3 attack. Basically, Silent Knight will be so silent that you won’t know he is in your card collection.
Argent Watchman cannot attack unless you use hero power. This is a really slow card with underwhelming stats when you consider the drawback. It is only good in a bad scenario when you have nothing to play on turn 3. In arena, it is slightly better than Ancient Watcher, so avoid it when possible.
Demonfuse and Flame Lance
Demonfuse is an awful card. It gives a mana crystal to your opponent and offers a miserable +3/+3 buff to a Demon in return. There is no reason to play Demonfuse. For the same cost, you already have more flexible Demonfire that buffs demons or deals damage to enemy minions.
If you enjoyed Pyroblasting minions, now you can do it for half the price. However, Polymorph removes big threats better then Flame Lance does. For 1 extra mana, it deals with Deathrattles, Divine Shields and infinite amount of health points. Still, there are no competitive Mage decks that run Polymorph today. This card will not see play outside of the arena.
Before the GvG expansion, we did not have a 3/4 minion for 3 mana and now, with TGT, these stats are becoming a standard. Spellslinger gives a random spell to both players. It fits well in a Flameweaker Tempo Mage deck. When playing this deck, you are dumping your hand as fast as possible, developing the board and efficiently removing enemy’s early threats. Many times you need just one more card for victory. Spells that Spellslinger provides can give that extra push you need. The fact that your opponent also gets a spell is not a big deal. A random spell in your almost empty hand is much more valuable to you than it is to your opponent when he has 6+ cards in his hand. In arena, I would pick Spider Tank over Spellslinger because, knowing my luck, I would end up giving Flamestrike to enemy.
Darnassus Aspirant is a 2 mana 2/3 that gives you an empty mana crystal and then takes it away when it dies. The obvious comparison is with Wild Growth, but Aspirant is better against aggressive decks. In addition to Wild Growth’s effect, it also puts a body on board. In fear of powerful minions played early, your opponent will use Frostbolt or Quick Shot to remove it. That can ruin their curve, lower their damage output and give you extra time to stabilize. In control matchup, where games also run after turn 10, Wild Growth seems like a better option. Excess Mana makes you feel less bad when drawing Wild Growth after turn 10. Darnassus Aspirant does not give you Excess Mana, which makes it worse in the late game. This minion is one of the worst you can get from Piloted Shredder. When it pops up, Battlecry effect does not trigger but Deathrattle does, destroying one of your mana crystals. In arena, it can be viewed as a better version of Mechwarper or Pint-Sized Summoner.
Wrathguard has nice 4/3 stats for 2 mana, but it comes with a drawback. When this minion takes damage, the same amount is dealt to your hero. Wrathguard can be played in aggressive versions of Zoo Warlock deck. That kind of decks is all about early board control and finishing the game fast, so extra damage to your hero from Wrathguard is not a big deal. Flame Imp, for example, deals 3 damage to your hero and is considered to be one of the best minions in Zoo. That being said, we will see Wrathguard that is Shield Slamed for 30+ damage in some youtube video. In arena, this card is not amazing. It dies from common 3/2 two mana drop. Damage to face can be crippling, if you are facing an opponent that is trying to rush you down with bunch of smaller minions. It is also bad in the late game, if your opponent has a big minion on board.
This panda bear is a 3/7 five mana cost minion. With Combo effect, it gains +3 attack becoming a Boulderfist Ogre. There is no competitive Rogue deck where Shado-Pan Rider currently fits. All Rogue constructed decks are combo driven. They usually want from their minions to draw cards, synergize with combo or help them survive early game against aggressive decks. Maybe we will see the rise of minion based Rogue in which this panda can find its place, but that is unlikely. In arena Shado-Pan Rider can be insane. You can coin it out and get Boulderfist Ogre on turn 4! That alone can win you the game.
Master of Ceremonies
Master of Ceremonies is a 4/2 minion that costs 3 mana. If you have minions with Spell Damage on board, Master of Ceremonies becomes 6/4 which is really good for a three mana drop. The problem is that minions with Spell Damage kinda suck. The only Spell Damage minions that are being played in constructed are Bloodmage Thalnos and Azure Drakes. Bloodmage Thalnos is a 1/1, so you cannot expect it to survive one turn. Playing 6/4 and 1/1 on turn 5 is good, but not amazing enough for constructed. Later in the game Master of Ceremonies is bad even if you trigger the effect. In arena, this card is 4/2 most of the time and that is bad.