AM + Footmen with Defend counters Fiends easily. Try to go Tier 2 faster than your opponent, and make Spell Breakers and Rifles if he has air. Also a few Priests to keep your SB's alive.
Just don't let your enemy make a expo. Build a farm near the free gold mines for scouting.
If your enemy is a noob hero focuser, make Paladin second to keep your AM alive. As long your AM is alive you can keep summoning Water Elementals which are even stronger than Crypt Fiends, and they are completely free.
Also, if you're a good player you could use the good old Zeppelin harass. Put 2 - 3 footmen into a Goblin Zeppelin and use them to attack Acolytes. If the enemy comes close or teleports, put footmen back into the zeppelin and go away. Repeat once he leaves his base. This will force your enemy make towers or gargoyles, which gives you an advantage. Not to mention how much gold he loses when he has to micro his Acos.
