Ok, i have to admit i am a bit crap at strategy games so i was a bit unsure about purchasing this. However i did and to begin with i found it very addictive and the gameplay balance was very good on the easiest difficulty, until i got to Leafshade.
You can't seem to build up a big enough army to split into 2 groups and if you wait and build about 40 units up evry time you try to attack the northern or eastern group the others sneak by and trash your base, any simple advice on how to get through this.
Are the later levels even harder ? as this is starting to put me off playing any further, just bought the fallout and earth series as well.

Its a matter of how you do it. One of the tips that people here gave me is to do as much as possible with your avatar before you claim any human/elf/dwarf monument. The enemy only start to get aggressive after you claim a monument so the more you can do with your heroes the better.
The main tactic I use on maps like that is to ignore making soldiers and focus entirely on building archer towers at chokepoints and keeping the hero stationed at the chokepoint to help fight anything that the towers don't kill
On this map, good chokepoints are at 4 & 10 as long as you can be careful enough to efficiently take out any bases that create troops that can approach from the sides.
One thing I've found invaluable is to station your units a moderate way back from the enemy, run the avatar forward & get a few enemies to notice you and pursue. You can lead them back to your main force and wipe them out
What sort of character are you playing?

Currently using a fire mage.

Hmm... I personally don't recall that map being particularly hard, as the starting area was quite defensible and the path forward was pretty linear. If you're finding it hard to split your units then I'd recommend building several crossbow towers backed up by a few troops to cut off one enemy stream, while using the bulk of your forces to wipe out an enemy encampment. Make sure you have enough clerics in your forces to keep casualties to near zero, mostly so you don't have to halt your advance while waiting for reinforcements. Also load up on marksmen, with just enough recruits to keep the enemies busy until the marksmen mow them down. Don't bother with enchanters or mentalists at this point; while they can be good once you have higher level forces, this early in the game they don't do all that much damage, die quickly, and the amount of Aria they require just isn't worth it.

I'm on the Whisper map and the only map so far that presented a bit of a challenge was Stoneblade Mountain. Make the wrong move, and you're in for some very rough times. Even more so with a spellcaster.
So regarding your question, i would say yes, there are a couple of maps a bit harder that Leafshade.
But stick with it. Some maps are great fun.
I'm also playing a pure spellcaster. Black Magic/Death + Elemental Magic/Ice.
Usually spellcasters have a hard time on early levels, but later on they kick ass :)

Yeah, Stoneblade was really rough. If it wasn't for loads of archer/frost towers I would have been wiped out early. As it was I had to die a time or two before I realized I should push forward and claim the dwarven monument and build a defensive position to stop the troll advance.
I also messed up by multi-classing my char: healer/death/elemental. By the time I max out my levels I won't be able to really deal damage like I could have if I would have only chosen two skills.

Actually, i managed to beat it with just 3 frost towers (plus army), and i only took the dwarven monument to get the iron for the 'Earthblade' sidequest, after clearing the map.
The 3 frost towers and 10-15 upgraded windarchers are enough to deal with the minotaurs incursions. That leaves your avatar and heroes and remaining army free to roam the map.
The key to this map is to take all the east (trolls) settlements as soon as possible. The avatar + 10 windarchers (upgraded) usually are more that enough (depending on the Avatar)
I'm a sucker for pure spellcasters chars, so usually i don't multiclass
So far i'm very happy with my blackmagic/death + elemental/ice and blackmagic/necromancy + elemental/fire chars

Ok. Can someone please give me a step by step (no, micro step by micro step) walkthrough of this map. It drives me insane. I'm playing on normal level and it looks like impossible to me. At first i tried to just go through the map with the forces i managed to gather and i even managed to get to the second human monument, but i din't attacked the orcs towers and the forces stationed there. I have run out of iron and was simply devasteted after 3 hours stuggling (not playing) on this map. Now i've tried to use towers tactic, but it is possilble to stop them, but not to advance. It seems that if only i build up a bit bigger force they start to generate enemies even faster and more. Wave after wave of 10-20 enemies every 15 seconds or so. How can i even think about destroying their bases if i can't cut through them and live. And iron is always a problem. And if i somehow manage to cut through those bases, i'm afraid what is waiting at the orcs towers. Normal difficulty? And someone is saying there will be even harder maps? maybe i shouldnt even try to play further? The only tactic so far that i found is moving forward 1 cm and building a tower. A path of towers.. huh..
On this screenshot there are ~20 of them running in just one wave and they will be coming and coming, and that's just after they have destroying another 50 units of my. Hate those games where enemies are generated in such dumb manner over and over again. They dont need to gather resources and my reinforces have to travel from my base.

Ok. I've managed to complete Leafshade map. As i said i was moving forward few meters and building a tower, then again a bit forward and a tower.. Took me very long and about 40 towers in total (some besides my base and bindstone). And i dont like such game. Now it's a Shiel. At first it was interesting, when i had to crash bandits small camps with 7 soldiers. But after i have eliminated alert posts i have to take Elven monument. But it is guarded by horde of minotaurs and goblins, so it is impossible to do this just with 7 soldiers. So i took the human monument below and.. again it started to generate hordes of goblins, orcs, bandits all of them flowing through my "base" (i cant even build anything, just towers, towers, towers..). WTF?! Is this game is similar further? Then i should delete this bullshit now and move on to some better games. This should be called Tower Defense. Or can you tell me what is your strategy in such situation?
Oh, and i hate that i have to order my own hero to attack all the time, though my own troops are being slaughtered just besides him.. Units are not reacting very fast to enemies often either.