This game is a lot harder than GC was but at the same time a couple of things can make it easier..
I have done pretty well already and a couple of tricks I have picked up.. (currently level 17)
Go back to the first level and win it on normal up to 60 times for the amulet (currently I have 20 wins amulet), do the same for sudden death (up to 20 too)..
The easiest one I have found so far is 'endurance'. Just start the level and lose it, you will quickly rack your way up to 60 wins in this class and get 5 amulets along the way giving you good amounts of XP (always over 1000) when sometimes just winning a hard level can only get you 300.
If you have the patience get to 60 with all game times you have unlocked as its easy points for not much work.
I am now up to the first Arcane Battle but haven't tried it yet at level 21..
Never forget to use your traps, poison traps are fantastic.
I can see why people are calling this hard but put a bit of effort in and you can get the levels done. I am playing at 3x speed just like I did in GC and still finishing levels up to this point so its not too terrible.
What part are you having trouble on? Have you unlocked the Sudden Death or Endurance battles yet? If so going back and doing those will get you some extra XP which is well needed.
Just done the first Arcane level at level 22 and it wasn't easy to kill the last guy. Most of the battle went smooth but when he came out I wasnt ready for him and died first time. He has about 30,000 HP and takes a lot of a beating so I had to make sure I had 5000 Mana and let him go around 3 times.
I've unlocked sudden death but can only do it on 2 of them. (one of them is the first, obviously), and I'm not even level 12, and don't know WHERE to get more exp, since I can't seem to stop them on sudden death.
OK, I've managed to get to the first level with a lost amulet (I could tell it was because it went into details on them), but can't survive the final wave >_>.