Hard to earn? no; it's hard to keep / have a decent buffer.
As you stated, one can get a lot of gold by spamming monday's daily, the problem is one burns thru it [B]fast[B], leveling platinum units over lv 50 is pain, blacks are even worse since they requiere more XP per level...
I do agree on the silver archers and gold, would also want AW or some pre-AW event if AW is not gonna happen yet
Recently rolled a Nanaly and i can't even CC her because i lack of silver archers
worse part is i have 3 rainbow fairies i want to feed her, but since she gets the quadshot after CC, i can't even do that... send help... i'm crying...